Repairing AR 3-A's

[Charles218]

About thirty years ago I had to sell my AR-3's. I was a poor college student and needed rent money. I have regretted doing this ever since and thought that I would never get another chance at these speakers. That changed today when I found a pair at my local reuse store, and I was suprised when I took them to the cashier and she told me $20 for the pair.

The cabinets are in very good shape, just minor scratches. I hooked them up and the woofers both work and I believe both mid-range speakers work, however the tweeters don't. I would like to check into having them brought up to spec but really don't know which way to turn. I am looking for suggestions from folks here on how to proceed. Is there a company/companies that specialize in authentic restoration? I would like to find a place within driving distance of Ann Arbor if possible, a couple hundred miles or so would be fine.

Also, I don't think that I would want to fix these and then sell them, but I would like to get some idea about their value. I just want to make sure that I don't spend 10 times their value on restoration. Any and all suggestions would be very helpful.

Thanks!!!

[dynaco_dan]

>About thirty years ago I had to sell my AR-3's. I was a poor

>college student and needed rent money. I have regretted doing

>this ever since and thought that I would never get another

>chance at these speakers. That changed today when I found a

>pair at my local reuse store, and I was suprised when I took

>them to the cashier and she told me $20 for the pair.

>

>The cabinets are in very good shape, just minor scratches. I

>hooked them up and the woofers both work and I believe both

>mid-range speakers work, however the tweeters don't. I would

>like to check into having them brought up to spec but really

>don't know which way to turn. I am looking for suggestions

>from folks here on how to proceed. Is there a

>company/companies that specialize in authentic

>restoration? I would like to find a place within driving

>distance of Ann Arbor if possible, a couple hundred miles or

>so would be fine.

>

>Also, I don't think that I would want to fix these and then

>sell them, but I would like to get some idea about their

>value. I just want to make sure that I don't spend 10 times

>their value on restoration. Any and all suggestions would be

>very helpful.

>

>Thanks!!!

Hi there;

I would suggest that you turn the tweeters pots back and forth a number of times with music playing.

This often cleans up the pot a bit and is considered a minimum temporary repair.

Good luck.

[charger3834]

I agree with Vern. Those pots really corode over time. The woofer needs to be removed, and the pot needs to be pulled apart and cleaned. Then you should be good to go.

[dynaco_dan]

>I agree with Vern. Those pots really corode over time. The

>woofer needs to be removed, and the pot needs to be pulled

>apart and cleaned. Then you should be good to go.

Hi again;

I was only suggesting to turns the pots first to see if particular issue might be dirty pots or not.

If that causes the tweeters to work then further work does need to be done later, such as the cleaning of the pots.

Do not attempt that just yet.

Removing an AR-3 grill cloth can damage or destroy the frame, cloth or mark the cabinetry.

If turning the pots doesn't work please tell us and further directions will be given by the many good members.

Good luck bargain hunter.

[Charles218]

>>I agree with Vern. Those pots really corode over time. The

>>woofer needs to be removed, and the pot needs to be pulled

>>apart and cleaned. Then you should be good to go.

>

>

>Hi again;

>

>I was only suggesting to turns the pots first to see if

>particular issue might be dirty pots or not.

>

>If that causes the tweeters to work then further work does

>need to be done later, such as the cleaning of the pots.

>

>Do not attempt that just yet.

>

>Removing an AR-3 grill cloth can damage or destroy the frame,

>cloth or mark the cabinetry.

>

>If turning the pots doesn't work please tell us and further

>directions will be given by the many good members.

>

>Good luck bargain hunter.

Hey Guys, thanks for the advice. I tried the speakers for a few minutes when I first brought them home and then disconnected them and carried them downstairs. I just don't have enough room upstairs for them along with my current speakers. I will have to bring them back up tomorrow and try the pots. When I did try them this afternoon, I messed with the treble controls on my preamp (Dyna Pat-4), as soon as I turned the treble control on the left channel the fuse on my power amp blew. It was kind of frightening as the speaker let out a loud pop. I have a Dyna 410 power amp, and I have a lot of respect for that kind of power.

[dynaco_dan]

>>>I agree with Vern. Those pots really corode over time. The

>>>woofer needs to be removed, and the pot needs to be pulled

>>>apart and cleaned. Then you should be good to go.

>>

>>

>>Hi again;

>>

>>I was only suggesting to turns the pots first to see if

>>particular issue might be dirty pots or not.

>>

>>If that causes the tweeters to work then further work does

>>need to be done later, such as the cleaning of the pots.

>>

>>Do not attempt that just yet.

>>

>>Removing an AR-3 grill cloth can damage or destroy the

>frame,

>>cloth or mark the cabinetry.

>>

>>If turning the pots doesn't work please tell us and further

>>directions will be given by the many good members.

>>

>>Good luck bargain hunter.

>

>

>Hey Guys, thanks for the advice. I tried the speakers for a

>few minutes when I first brought them home and then

>disconnected them and carried them downstairs. I just don't

>have enough room upstairs for them along with my current

>speakers. I will have to bring them back up tomorrow and try

>the pots.

When I did try them this afternoon, I messed with

>the treble controls on my preamp (Dyna Pat-4), as soon as I

>turned the treble control on the left channel the fuse on my

>power amp blew.

Hi Charles;

Power or speaker fuse?

Fast blow or slow blow fuse?

What amperage was the fuse?

Wait before retrying anything else, you don't normally blow a fuse doing just that.

Perhaps the speaker wires were shorted?

Good topic, and good luck.

All the very best in 2006 to you and yours, Charles.

It was kind of frightening as the speaker let

>out a loud pop. I have a Dyna 410 power amp, and I have a lot

>of respect for that kind of power.

[Charles218]

>>

>>Hey Guys, thanks for the advice. I tried the speakers for a

>>few minutes when I first brought them home and then

>>disconnected them and carried them downstairs. I just don't

>>have enough room upstairs for them along with my current

>>speakers. I will have to bring them back up tomorrow and

>try

>>the pots.

>

>When I did try them this afternoon, I messed with

>>the treble controls on my preamp (Dyna Pat-4), as soon as I

>>turned the treble control on the left channel the fuse on my

>>power amp blew.

>

>

>

>Hi Charles;

>

>Power or speaker fuse?

>

>Fast blow or slow blow fuse?

>

>What amperage was the fuse?

>

>Wait before retrying anything else, you don't normally blow a

>fuse doing just that.

>

>Perhaps the speaker wires were shorted?

>

>Good topic, and good luck.

>

>All the very best in 2006 to you and yours, Charles.

>

>

> It was kind of frightening as the speaker let

>>out a loud pop. I have a Dyna 410 power amp, and I have a

>lot

>>of respect for that kind of power.

>

Vern,

It was the power amp fuse that blew. I was adjusting the treble on the right channel and the right channel power amp fuse blew at exactly the moment that I turned the control. I wanted to turn the treble all the way up to make sure that I was correct in thinking that the tweeter was not working.

I know that it was a fast blow fuse as I just had them out the other day trying to track down a short in the system. I don't know the amperage and I tossed it so can't check to see. I replaced the fuse with a 3 amp fuse, left the tone controls alone and the speaker worked normally, just without the tweeter. Since it now worked with a new fuse, I think we eliminate shorted speaker wires as a problem.

This seemed strange to me also and maybe is not at all connected to the speaker. I rarely use the tone controls at all, this may have been the first time in years that it has been touched and I suspect that the treble control may be the issue here. I will haul the speakers back upstairs later today and fuss with the speaker pots and see where that takes me.

Thanks for your observations and assistance.

[soundminded]

First of all, congratulations on this find. This was among the finest and most respected high fidelity loudspeakers during its period of production. It may cost more to restore than their fair market value but many of us who post here believe it is worth it because when you are done, you will have something unique which can give many years of pleasure.

Don't connect this speaker to a high powered amplifier again until you are sure of its reliability. Doing that risks damage to both the amplifier and components in the speaker which are not already damaged or defective. Here are some areas to look at which would cause concern to those of us experienced with this model due to its age.

Inspect the woofer surrounds carefully. Any sign of deterioration is a signal to have the surrounds replaced. The air tightness of the system is critical to its proper operation.

It is almost certain that if the potentiometers have not already been replaced or cleaned, they will need to be. Corrosion of their contacts is typical making operation of the midrange and tweeter drivers first intermittent and then rendering them completely inoperative.

The electrolytic capacitors in the crossover network will likely need replacement. A chemical reaction over time causes them to change value actually often becoming higher. This not only changes the overall sound, it risks damage to the midrange and tweeter drivers. Also check the midrange and tweeter drivers to determine if they operate properly. Electical damage to the tweeter can often be repaired with a replacement voice coil.

If you are skilled, you can do this work yourself at relatively modest cost. Otherwise, it is better to leave it in the hands of someone who is. The quality of the result will depend on the quality of the work done in restoration. If you feel it is more time, money, and trouble than it's worth, consider selling it to someone who feels otherwise. Those of us who post here like to think that as many of the limited supply of these out there as possible are still in use.

Good Luck

[Charles218]

>First of all, congratulations on this find. This was among

>the finest and most respected high fidelity loudspeakers

>during its period of production. It may cost more to restore

>than their fair market value but many of us who post here

>believe it is worth it because when you are done, you will

>have something unique which can give many years of pleasure.

>

>

>Don't connect this speaker to a high powered amplifier again

>until you are sure of its reliability. Doing that risks

>damage to both the amplifier and components in the speaker

>which are not already damaged or defective. Here are some

>areas to look at which would cause concern to those of us

>experienced with this model due to its age.

>

>Inspect the woofer surrounds carefully. Any sign of

>deterioration is a signal to have the surrounds replaced. The

>air tightness of the system is critical to its proper

>operation.

>

>It is almost certain that if the potentiometers have not

>already been replaced or cleaned, they will need to be.

>Corrosion of their contacts is typical making operation of the

>midrange and tweeter drivers first intermittent and then

>rendering them completely inoperative.

>

>The electrolytic capacitors in the crossover network will

>likely need replacement. A chemical reaction over time causes

>them to change value actually often becoming higher. This not

>only changes the overall sound, it risks damage to the

>midrange and tweeter drivers. Also check the midrange and

>tweeter drivers to determine if they operate properly.

>Electical damage to the tweeter can often be repaired with a

>replacement voice coil.

>

>If you are skilled, you can do this work yourself at

>relatively modest cost. Otherwise, it is better to leave it

>in the hands of someone who is. The quality of the result

>will depend on the quality of the work done in restoration.

>If you feel it is more time, money, and trouble than it's

>worth, consider selling it to someone who feels otherwise.

>Those of us who post here like to think that as many of the

>limited supply of these out there as possible are still in

>use.

>

>Good Luck

I read your post above just as I was about to carry the 3's back upstairs to give them another try, and I have been slowed by your cautions. I use the amp on a regular basis with KLH Model 4's, a speaker in the same size range as the AR's. Like the AR's they are also acoustic suspension. While I m not very knowledgeable about electronics, I am a musician by trade, I suspect that the amp system is okay. I have had it and used it for about fifteen trouble free years.

I have not the slightest idea how to get into this speaker system and am not inclined to learn now, most of my DIY projects are branded with my amateur mistakes. I have the same sense of respect for these speakers that your message so wonderfully states, and would be most comfortable having a like minded technician evaluate these speakers for me. So back to part of my original question, how to I find a quality shop or repair person to restore these for me? And, what would the fair market value be for these speakers once restored?

During my short listening session yesterday, I heard for the first time in these many years the wonderful smoothness and open relaxed bass that I remember from my first pair many years ago. I would like to get these back into shape and have that sound to listen to everyday. I am aware that this is probably my last chance, heck it has taken thirty plus years for these to come along, and my highest priority is to not take any short cuts and get it done correctly.

Thanks!!!

[soundminded]

Dynaco 416 is a very rugged amplifier and is well protected from abuse however, as Dynaco stated in the assembly manual of my Stereo 120, it is best not to tempt fate. If you must use this amplifier, set the Dynaguard at its lowest setting and be very cautious with the volume control. Blowing a fuse was a warning that should not go unheeded. Something is probably very wrong, possibly a short circuit or a capacitor which is failing intermittently when voltage is high enough, certainly a very low load impedence at some frequencies. You can get added protection by installing a small fuse, say 1 or 2 amps in series with the speaker at least until you are sure of its reliability. There's an old saying among repair technicians, a $300 picture tube protected a 10 cent fuse.

As for restoration, there are a number of sources referenced on this site. Other contributors can be more helpful in choosing one close to you. You might also contact Madisound which is in Madison Wisconsin, maybe not too far from Ann Arbor. They may offer services or refer you to competent nearby restorers.

[Charles218]

Well, I couldn't resit the temptation to try one more listening session. After working each of the pots back and forth several times and with judicious use of the volume control, I hooked up the speakers again. Working the pots back and forth made a difference, I can now clearly tell that the bass, mid-range, and tweeter on each speaker is working. Thank you for the tip. I will continue to seek out a repair facility. If someone does find these 3-A's for sale someone, please note the price and let me know.

[dynaco_dan]

>Well, I couldn't resit the temptation to try one more

>listening session. After working each of the pots back and

>forth several times and with judicious use of the volume

>control, I hooked up the speakers again. Working the pots

>back and forth made a difference, I can now clearly tell that

>the bass, mid-range, and tweeter on each speaker is working.

>Thank you for the tip. I will continue to seek out a repair

>facility. If someone does find these 3-A's for sale someone,

>please note the price and let me know.

>

>

Hi again Charles;

I was certain you had said you used a Dynaco 410 amp.

The fuse you removed and you said it was the power amp fuse and fast blow.

You cannot use fast blow fuses in your main primary 120 volt fuse for one thing.

Replace this singular fuse with the correct rated slow blow fuse.

How did you know it was a fast blow fuse?

I can dig up all this information if required, I believe that the power fuse will probably be a least 10 - 15 amps slow blow.

The Dynaco 400 and 416 had a 15 amp circuit breaker rather than a fuse.

Definitely don't just go ahead and do this without we follow up my information more thoroughly.

I don't know how a 3 amp fast blow fuse would get into any socket on that amp.

Unless there is 3 sockets, one for AC power and two speaker fuseholders externally.

This fuse would have had to be in a speaker fuseholder then.

If you can take a few closup photos that would be great.

My 410 is still packed up so I can't look at my cabinet.

I don't think the 410 had speaker fuses externally.

The 400 and 416 did, as well as Dynaguard.

The 410 is a plain Jane 400 without all the frills.

I read somewhere not too long ago, that someone preferred the sound of the 410 to the 400.

The AC power fuseholder should be almost kissing the power cord where it enters the cabinet.

Speaker fuseholders, if there is some, will be almost kissing the speaker terminals.

Good luck.

All the very best in 2006 to you and yours.

As was already written, you got a super deal on a great classic speaker system.

[Charles218]

>Hi again Charles;

>

>I was certain you had said you used a Dynaco 410 amp.

>

>The fuse you removed and you said it was the power amp fuse

>and fast blow.

>

>You cannot use fast blow fuses in your main primary 120 volt

>fuse for one thing.

>

>Replace this singular fuse with the correct rated slow blow

>fuse.

>

Hi Vern,

Let me address a couple of your points, and keep in mind I'm a musician not an enigneer.

The amp is the Dyna 410, I actually have the original manual for it. The fuses that I was referring to are the speaker fuses on the amp. and as you know there is one for each speaker. Maybe I jumped the gun when I said they were fast blow, but I thought that slow blow fuses had a relative thick wire. The fuse that blew had a "very" thin wire link, so I assumed fast blow, please let me know if my assumptions are off here.

The Dyna's manual has a section on "Loudspeaker Fusing" and says that the amp comes with a 5 amp, 3AG fuse. It further states that this fuse "will not fail when the amplifier is operated at full power (200 watts into 8 ohms), and therefore they provide NO PROTECTION for your speakers."...... A slo-blo fuse will allow appreciably more overdrive than the same value standard fast-blow type, and is thus not generally recommended for speaker protection." Next in this section of the manual there is a chart with various amp fuses and various speaker ohm ratings. So I put a 3 amp fuse in to replace the one that blew.

Another area that I forgot to mention. Several years ago I installed a Niles SP4 Speaker Selection Switch and several Russound In-Wall Stereo Volume Controls. This means that all of my hi-fi signals go through the selector switch and the volume controls. I have four sets of speakers around the house, all vintage AR & KLH, and wanted to have each set have access to my main system. From my understanding these volumes controls and the selector switch are all solid, high quality items.

So to recap, the fuse that blew when I tried to boost the treble output was the right channel speaker fuse. My guess is that since I have rarely use the tone controls, there was dirt on the control which led to the large pop and the fuse blowing. It seems that the blown fuse was a pre-amp/power amp issue and not related to the speaker.

Thanks again for your assistance!!!

[dynaco_dan]

>>Hi again Charles;

>>

>>I was certain you had said you used a Dynaco 410 amp.

>>

>>The fuse you removed and you said it was the power amp fuse

>>and fast blow.

>>

>>You cannot use fast blow fuses in your main primary 120 volt

>>fuse for one thing.

>>

>>Replace this singular fuse with the correct rated slow blow

>>fuse.

>>

>Hi Vern,

>

>Let me address a couple of your points, and keep in mind I'm a

>musician not an enigneer.

>

>

>

>The amp is the Dyna 410, I actually have the original manual

>for it. The fuses that I was referring to are the speaker

>fuses on the amp. and as you know there is one for each

>speaker. Maybe I jumped the gun when I said they were fast

>blow, but I thought that slow blow fuses had a relative thick

>wire. The fuse that blew had a "very" thin wire link, so I

>assumed fast blow, please let me know if my assumptions are

>off here.

>

>The Dyna's manual has a section on "Loudspeaker Fusing" and

>says that the amp comes with a 5 amp, 3AG fuse. It further

>states that this fuse "will not fail when the amplifier is

>operated at full power (200 watts into 8 ohms), and therefore

>they provide NO PROTECTION for your speakers."...... A slo-blo

>fuse will allow appreciably more overdrive than the same value

> standard fast-blow type, and is thus not generally

>recommended for speaker protection." Next in this section of

>the manual there is a chart with various amp fuses and various

>speaker ohm ratings. So I put a 3 amp fuse in to replace the

>one that blew.

>

>Another area that I forgot to mention. Several years ago I

>installed a Niles SP4 Speaker Selection Switch and several

>Russound In-Wall Stereo Volume Controls. This means that all

>of my hi-fi signals go through the selector switch and the

>volume controls. I have four sets of speakers around the

>house, all vintage AR & KLH, and wanted to have each set have

>access to my main system. From my understanding these volumes

>controls and the selector switch are all solid, high quality

>items.

>

>So to recap, the fuse that blew when I tried to boost the

>treble output was the right channel speaker fuse. My guess is

>that since I have rarely use the tone controls, there was dirt

>on the control which led to the large pop and the fuse

>blowing. It seems that the blown fuse was a pre-amp/power amp

>issue and not related to the speaker.

>

>Thanks again for your assistance!!!

Hi Charles;

Whoa!

The speaker fuse is to protect a set or pair of speakers not more than that.

If you are adding additional speakers the impedance may or may not drop.

There is much more knowledgeable members that will jump in and comment after I am finished.

For your information I can't remember if the 410 had speaker fuses or not.

You are correct about the fast versus slow, thick versus hairlike fuses.

You now want to fuse a single pair of speakers only which will use fast blow, BUT, a guestimated size will be needed here.

AR recommended the FNM series slow blow fuses in the open style cartridge.

They never recommended a fast fuse size so another issues comes up.

The slow blow fuses are expensive and difficult to find.

If you go to the Crownaudio.com website they have a very good article on power handling and fusing speakers, well worth reading.

Way back when AR sold the fuses at their cost, for about 3 for $1.00, including postage, there was not a lot of information about fusing or speaker cable sizing.

After reading the Crownaudio article, I reasoned that they were suggesting fast blow fuses for the uppers, and slow blow fuses for the woofers.

As you may well know, there isn't a lot of speakers, that have a built in fuseholder, never mind a dual set.

The slow blow fuse, FNM type, as per AR, will protect mostly the woofer, which draws the most power.

It doesn't really protect the uppers.

A fast blow fuse to protect the uppers, will blow too soon because of the woofers draw.

Go back to the option screen for the different manufacturers and go down to "others", open that topic, follow it down to, "fast blow fuses", which I started in Nov/05, and Dec 24/05 I updated it again.

Unless someone else comes forward with more current or accurate information, you can use that fusing data.

The non-desirable slow blow fuses that will fit into those 1/4" x 1 1/4" fuseholders are of a different characteristics than the FNM type and so should not be used.

The other goodies that you have I am not experienced with to offer any advice on.

My only comment is disconnect anything other than your 2 stereo main speakers from the amplifier and start with only 1 amp fast blow speaker fuses.

When you add additional loads to the amp the impedance drops.

Some other member may say what you have is ok, but, until that happens, use only the one pair.

When you told us you were boosting the treble, you were boosting the treble for all of those speakers, maybe.

Good luck again.

[Charles218]

>Hi Charles;

>

>Whoa!

>

>The speaker fuse is to protect a set or pair of speakers not

>more than that.

>

>If you are adding additional speakers the impedance may or may

>not drop.

>

>There is much more knowledgeable members that will jump in and

>comment after I am finished.

>

>For your information I can't remember if the 410 had speaker

>fuses or not.

>

>You are correct about the fast versus slow, thick versus

>hairlike fuses.

>

>You now want to fuse a single pair of speakers only which will

>use fast blow, BUT, a guestimated size will be needed here.

>

>AR recommended the FNM series slow blow fuses in the open

>style cartridge.

>

>They never recommended a fast fuse size so another issues

>comes up.

>

>The slow blow fuses are expensive and difficult to find.

>

>If you go to the Crownaudio.com website they have a very good

>article on power handling and fusing speakers, well worth

>reading.

>

>Way back when AR sold the fuses at their cost, for about 3 for

>$1.00, including postage, there was not a lot of information

>about fusing or speaker cable sizing.

>

>After reading the Crownaudio article, I reasoned that they

>were suggesting fast blow fuses for the uppers, and slow blow

>fuses for the woofers.

>

>As you may well know, there isn't a lot of speakers, that have

>a built in fuseholder, never mind a dual set.

>

>The slow blow fuse, FNM type, as per AR, will protect mostly

>the woofer, which draws the most power.

>

>It doesn't really protect the uppers.

>

>A fast blow fuse to protect the uppers, will blow too soon

>because of the woofers draw.

>

>Go back to the option screen for the different manufacturers

>and go down to "others", open that topic, follow it down to,

>"fast blow fuses", which I started in Nov/05, and Dec 24/05 I

>updated it again.

>

>Unless someone else comes forward with more current or

>accurate information, you can use that fusing data.

>

>The non-desirable slow blow fuses that will fit into those

>1/4" x 1 1/4" fuseholders are of a different characteristics

>than the FNM type and so should not be used.

>

>The other goodies that you have I am not experienced with to

>offer any advice on.

>

>My only comment is disconnect anything other than your 2

>stereo main speakers from the amplifier and start with only 1

>amp fast blow speaker fuses.

>

>When you add additional loads to the amp the impedance drops.

>

>Some other member may say what you have is ok, but, until that

>happens, use only the one pair.

>

>When you told us you were boosting the treble, you were

>boosting the treble for all of those speakers, maybe.

>

>Good luck again.

>

Vern,

I am getting a little past my expertise here but I think I see what you are getting at. Here is what my set-up looks like.

I have a Dyna PAT-4 Pre-amp going to the Dyna 410 power amp. From the power amp output the signal goes to a Niles Speaker Selector Switch. With this selector box I can select from 1 to 4 pairs of speakers to drive. That is, I can listen to just one pair or up to four pair, all at the same time. The selector selector switch is a Niles SS-4, here are part of the specs for this unit -

FEATURES

* Power Handling: 100 Watts Per Channel RMS, 200 Watts Peak

* Protection Circuit Safeguards Receiver/amplifier

* Separate Left And Right Ground Paths For Compatibility With All Amplifiers, Including Bridged Designs

For my testing of the new AR's yesterday I only had the AR's selected, the other speakers were out of the circuit.

When the signal leaves the "Speaker Selector Switch" it goes to a volume control so that the volume of each pair of speakers can be controlled separately, and from there on to the speakers. The volume controls are made by Russound, they are designated as "ALTx UltraMatch Volume Control". In reading the instructions, this is what I see, "The UltaMatch volume control provides a method of matching the minimum output impedance of the amplifier or speaker selector or impedance matching equipment."

Now to be honest, I am not sure how or if this relates to your concern "The speaker fuse is to protect a set or pair of speakers not more than that." I am sure that with all of this extra equipment in the circuit that I am degrading the signal, but that is not of utmost importance to me so I live with it.

Yes the 410 has two speaker fuses, and as you noted the "Speaker fuseholders, if there is some, will be almost kissing the speaker terminals.", that is what I have. I will change the set-up and connect directly to the speakers and experiment with different fuses, I think that is a good idea. And yes, "if" I had more then one set of speakers selected adjusting the treble would affect all of the speakers. But as I mentioned earlier I only had the AR 3's selected. But I think that my first priority will be to find a respectable shop that has the same respect for these speakers that you and the many others on this forum have. Now that I know that all of the drivers work, I would love to make sure that all of the components are checked out and repaired as needed. So I am still searching for a shop or person who can handle this job.

Thanks!!!

[Pete B]

Hi Charles,

I've not followed this thread completely but I'd like to offer some input. I have a PAT-4 that I've not used in a long time, and I built at least one from the kit many years ago. There are a few possiblities, none are good, when a fuse blows on touching the treble control. One is that it burst into oscillation, due to dirty contacts, old caps, can't say for sure, another is that some large DC pulse was put out because of leaky caps, or that you had static discharge that caused an output pulse. The PAT-4 has many electrolytic caps in the signal path, and they should probably be replaced if you've not done it already. Several are 1 uF if IIRC and I'd use low cost film types here, I think the output cap is 50 uF and it would probably not hurt to use a 10 or 20 uF film type here if you can't fit a 50 uF film, as long as your not driving very low impedance loads. Deoxit on the switches and controls is a good idea also.

The Dynaco 410 if I remember this model correctly, does not drive reactive 4 ohm loads well, they upgraded it to the 416 where they doubled the number of output devices and probably adjusted the current limiting circuits. It probably could also use to be gone over being so old, unless you already have.

Definately fuse if you don't go over this equipment and at least apply some spray cleaner.

Pete B.

[Pete B]

It's an interesting coincedence that for several months I've been thinking that re-capping our old Dyna PAT-4 would be a good project for my youngest son. Talking here about it made me get it out and take a look.

The coupling caps are 1 uF, 5 uF, 50 uF, and a 320 uf emitter resistor bypass cap. This factory built PAT-4 was given to me, and the friend said it doesn't sound right. Looking at it now I see that there are some small disk ceramic capacitors tacked on the back of the PC board from the base to the collector of the first transistor in the line amp. To be honest, I only have a vague memory of this but the lettering on them looks familiar and I'm fairly certain that I put them there. There are no other mods to this unit and I'm not the type to put them in if there wasn't a problem. It's very likely that I took a look at it with a scope and found instabitlity under some conditions. Sorry, I don't remember more.

It is interesting that many of the old power amps back in the day that had a reputation for blowing up, might have been fed ultrasonic, high frequency garbage from poorly designed preamps that caused their fairlure. Oscillations in the system could also be a cause of tweeter failure.

Soldering of all the chassis wiring looks clean, the circuit boards have many connections with too much solder that should probably be cleaned up.

Pete B.

[Charles218]

>Hi Charles,

>

>I've not followed this thread completely but I'd like to offer

>some input. I have a PAT-4 that I've not used in a long time,

>and I built at least one from the kit many years ago. There

>are a few possiblities, none are good, when a fuse blows on

>touching the treble control. One is that it burst into

>oscillation, due to dirty contacts, old caps, can't say for

>sure, another is that some large DC pulse was put out because

>of leaky caps, or that you had static discharge that caused an

>output pulse. The PAT-4 has many electrolytic caps in the

>signal path, and they should probably be replaced if you've

>not done it already. Several are 1 uF if IIRC and I'd use low

>cost film types here, I think the output cap is 50 uF and it

>would probably not hurt to use a 10 or 20 uF film type here if

>you can't fit a 50 uF film, as long as your not driving very

>low impedance loads. Deoxit on the switches and controls is a

>good idea also.

>

>The Dynaco 410 if I remember this model correctly, does not

>drive reactive 4 ohm loads well, they upgraded it to the 416

>where they doubled the number of output devices and probably

>adjusted the current limiting circuits. It probably could

>also use to be gone over being so old, unless you already

>have.

>

>Definately fuse if you don't go over this equipment and at

>least apply some spray cleaner.

>

>Pete B.

Hello Pete,

I think that your take on all of this is right on. I have had the 410 and PAT-4 for several many years and have just used them, probably never opened them up. Finding these AR-A's is probably going to make a major dent in my schedule. I would love nothing more then to get the amps, I also have one or two PAS-3's sitting around somewhere, and speakers back in pristine shape. While I am really on the outside of the circle as far as the electronics, I did build several Dyna units and would get much satisfaction out of working on these myself. I will need to see if I can find clear, precise step by step directions on how to proceed.

[Pete B]

I've started to take a closer look at this old PAT-4. I think I used this unit in the garage for a while. Cleaned it with Deoxit spray, amazing how hard it is to get the oxidation off the old tin plated RCA jacks.

I do remember that when I put that cap in on the first stage transistor, I did it in a rush, and now looking at the schematic notice that the second transistor stage already has a dominant pole cap in place making that cap I put in a bad idea, I removed it for now. I remember that it was fairly difficult to get the unit to oscillate. The preamp has a lot of bandwidth to produce those nice square waves in the marketing literature and there is no RF rejection filter. I'll try to take another look at it after I install some new caps to replace the old electrolytics.

Pete B.

>It's an interesting coincedence that for several months I've

>been thinking that re-capping our old Dyna PAT-4 would be a

>good project for my youngest son. Talking here about it made

>me get it out and take a look.

>

>The coupling caps are 1 uF, 5 uF, 50 uF, and a 320 uf emitter

>resistor bypass cap. This factory built PAT-4 was given to

>me, and the friend said it doesn't sound right. Looking at it

>now I see that there are some small disk ceramic capacitors

>tacked on the back of the PC board from the base to the

>collector of the first transistor in the line amp. To be

>honest, I only have a vague memory of this but the lettering

>on them looks familiar and I'm fairly certain that I put them

>there. There are no other mods to this unit and I'm not the

>type to put them in if there wasn't a problem. It's very

>likely that I took a look at it with a scope and found

>instabitlity under some conditions. Sorry, I don't remember

>more.

>

>It is interesting that many of the old power amps back in the

>day that had a reputation for blowing up, might have been fed

>ultrasonic, high frequency garbage from poorly designed

>preamps that caused their fairlure. Oscillations in the

>system could also be a cause of tweeter failure.

>

>Soldering of all the chassis wiring looks clean, the circuit

>boards have many connections with too much solder that should

>probably be cleaned up.

>

>Pete B.