KLH Twenty One restoration

[npt3]

So, I was at Brimfield yesterday and found a Twenty One in not-bad-at-all condition (excellent cosmetics on the front panel, grille cloth, dial and knobs, veneer quite restorable), so for $40 I thought it was a good pickup.  I was told it doesn't power up, and by gum it doesn't (the fuse doesn't look blown, though), so I'll get to work on it for my late summer project!

 

I think JKent is quite experienced with the 21, but if anyone has some tips of the "low-hanging fruit" variety, feel free to share.

[JKent]

Nice radio but full disclosure: I don't have a lot of technical expertise. I just bought one in similar condition--nice cosmetics but not working. Mine's a 21/II. I replaced a dried out power cord and the 2000uF filter cap but still no go, so it's off to Tim at Bristol Electronics. He'll have it good-as-new.

btw, don't just go by appearance on that fuse. Check the continuity. Good luck and keep us posted.

Kent

[npt3]

Thanks for the clarification! 😎

[JKent]

"Before" it was filthy, grille cloth was faded, cord was stiff and a knob was missing. Pretty now but needs work.....

[npt3]

I'm thinking of re-doing the grille.  I've got some nice Guilford acoustic fabric choices, but the back of the grille (which I think is an earlier manufacture) has a dark, thin, pretty transparent fabric over the speaker opening. 

Does anyone know what this fabric is called?  (in case I need to have some on hand for, you know, emergencies)

[JKent]

I think it's called scrim but I'd skip it.

[JKent]

KLH actually made FIVE different radios, all called the “Twenty-One” (always spelled out). In chronological order:

1. The original Twenty-One replaced the tube Model Eight around 1965. It was all transistor with a walnut veneer cabinet, beige knobs and a beige/white plastic grille.
2. The Twenty-One/II came out around 1969 after Singer bought KLH. It was essentially identical to the original but had a black cloth grille, black/silver knobs and the “Waller” tuner.
3. The Twenty-One FM came out in the early ‘70s. It was larger, had a vinyl clad cabinet and a foam grille (that always disintegrated).
4. The Twenty-One AM/FM. Same thing, with AM.
5. The Twenty-One CL. Clock radio. The largest of the three later Twenty-Ones, had a flip-type clock that had about a 99% failure rate.

The AM/FM is missing from this picture but it just like the 21-FM (3rd from top) except it has AM on the dial along with the FM., like the CL on the bottom.

[npt3]

I had the CL once.  I thought it was a far cry in build quality from the 'real' (i.e., pre-Singer) radios (I mean, "receiving systems.")  And the clock was indeed crap.

My copy of the Twenty-One manual shows the grille cloth to be pretty much all white, i.e., no contrasting accent threads.  I have yet to see one where the grille cloth hasn't yellowed, which isn't surprising given that these little guys are pushing 60.

Since mine is not working, (I have a working one, also) I think I'm going to use it for some experimentation.  Knowing that the cloth has yellowed and somehow shrunk (horizontally) over the years, I'm going to try to very gently remove it from the masonite, whiten it, and see if I can't stretch it another couple of millimeters.  I'm going to re-cover it with new fabric (again, as a learning exercise), but it's worth a shot.

 

[JKent]

That original plastic grille was 2-tone white and sort of cream. It shrinks and I've tried stretching it without success. What I have done is a cut & paste job that works OK or I found some vinyl placemats that looked pretty close. 1st pic below shows the placemat on top, original on the bottom. 

The 2nd and 3rd photos show the jigsaw puzzle I did with the original grille material. btw, looking through some old photos I see I did replace the scrim on the back of the masonite (3rd pic).

[npt3]

1 hour ago, JKent said:

That original plastic grille was 2-tone white and sort of cream. It shrinks and I've tried stretching it without success. What I have done is a cut & paste job that works OK or I found some vinyl placemats that looked pretty close. 1st pic below shows the placemat on top, original on the bottom. 

The 2nd and 3rd photos show the jigsaw puzzle I did with the original grille material. btw, looking through some old photos I see I did replace the scrim on the back of the masonite (3rd pic).

I think I'm going to try the jigsaw technique, Kent.  My grille cloth is in really good shape, so it should look pretty great. 

Where did you get your scrim material?

[JKent]

It was salvaged from some other speakers

[npt3]

I'm really enjoying my journey of discovery in the Land Of The Twenty-One!  Over the past couple of years I've tackled much larger projects (e.g., my Citation Receiver resto), so it's refreshing to work on something more modest and...discrete.  It also helps that Henry K. must have cranked out at least as many of these gems as AR did XAs.

Anyway, I've got a couple of units now to work with, so I can work towards restoring my 'best' with the cleanest parts, and I'm taking my time with it.  I want to first do no harm, but I'm also thinking that while I have access to the insides, I should get my radio ready for the next 50 years by recapping at least the amplifier board.

The other thing I want to get in shape is the speaker.  I've got a bottle of sealant (thanks Roy!) to treat the surround, and again here, the speaker is working well and the surround seems in great shape (in all of my units) but I'm going to do it and get it over with.

[npt3]

On 2/2/2022 at 7:23 PM, npt3 said:

I'm really enjoying my journey of discovery in the Land Of The Twenty-One!  Over the past couple of years I've tackled much larger projects (e.g., my Citation Receiver resto), so it's refreshing to work on something more modest and...discrete.  It also helps that Henry K. must have cranked out at least as many of these gems as AR did XAs.

Anyway, I've got a couple of units now to work with, so I can work towards restoring my 'best' with the cleanest parts, and I'm taking my time with it.  I want to first do no harm, but I'm also thinking that while I have access to the insides, I should get my radio ready for the next 50 years by recapping at least the amplifier board.

The other thing I want to get in shape is the speaker.  I've got a bottle of sealant (thanks Roy!) to treat the surround, and again here, the speaker is working well and the surround seems in great shape (in all of my units) but I'm going to do it and get it over with.

I'm having second thoughts on recapping.  😂  Honestly, the electrolytics look really, really good, not leaky at all like I've seen in some receiver disasters.  I know that after 50 or so years they'll "go", but am I just putting off the inevitable by leaving them where they are?

[JKent]

If it ain’t broke don’t fix it 😉

otoh the 2000uF power supply cap is easily accessible and a cause of hum so I always replace those.

ere are pics of a bad 2k cap, much smaller 2200uF replacement and a labeled pic of the audio board (just because I hd it). If you want a pdf copy of the Service Manual PM me with your email address.

[JKent]

Here are Henry's radios and their progeny. The 21/II, 21 FM, 21 AM/FM and the 21 CL are Singer era products. Late in his career Kloss designed the Tivoli One, with obvious KLH roots.

The AM/FM wasn't in the collage, so the 2nd pic shows that model. Looks just like the 21-FM.

 

[npt3]

42 minutes ago, JKent said:

If it ain’t broke don’t fix it 😉

otoh the 2000uF power supply cap is easily accessible and a cause of hum so I always replace those.

ere are pics of a bad 2k cap, much smaller 2200uF replacement and a labeled pic of the audio board (just because I hd it). If you want a pdf copy of the Service Manual PM me with your email address.

Eek!  My filter caps don't look THAT bad, lol.  I'm all about less hum, and the filter cap's easy enough to replace, so: off to Mouser

[npt3]

6 minutes ago, npt3 said:

Eek!  My filter caps don't look THAT bad, lol.  I'm all about less hum, and the filter cap's easy enough to replace, so: off to Mouser

PS I've got a copy of the Service Manual, Kent, thanks!

[JKent]

11 minutes ago, npt3 said:

off to Mouser

FWIW my tech always uses Panasonic caps for their quality and reliability. That blue cap is some cheapy I bought before learning better. 2200uF 35V is a good replacement and use a cap rated for at least 105°C

[npt3]

On 2/5/2022 at 12:03 PM, JKent said:

FWIW my tech always uses Panasonic caps for their quality and reliability. That blue cap is some cheapy I bought before learning better. 2200uF 35V is a good replacement and use a cap rated for at least 105°C

I ordered a couple of the higher quality Panasonics and a couple of the higher quality Nichicons to those specs.  👍

[npt3]

On 2/5/2022 at 11:35 AM, JKent said:

Here are Henry's radios and their progeny. The 21/II, 21 FM, 21 AM/FM and the 21 CL are Singer era products. Late in his career Kloss designed the Tivoli One, with obvious KLH roots.

The AM/FM wasn't in the collage, so the 2nd pic shows that model. Looks just like the 21-FM.

 

I always liked the Braun-like styling of the Model One.  I had a Model Two (with the subwoofer) in my office for many years, and I just loved it to death.  When I stopped having an office office, I sadly parted with it, but I got to spend almost twenty years with it.  A great relationship!

[npt3]

Just now, npt3 said:

I always liked the Braun-like styling of the Model One.  I had a Model Two (with the subwoofer) in my office for many years, and I just loved it to death.  When I stopped having an office office, I sadly parted with it, but I got to spend almost twenty years with it.  A great relationship!

[npt3]

So, I'm having a pause before treating my driver surrounds with Roy C's sealant.  Is there any downside to NOT doing it?  (I only ask because the driver I want to treat has a really nice, clean and translucent surround that does not appear to be degraded or damaged in any way.) 

(I know that sealing KLH surrounds is a popular topic, so my apologies in advance for possibly flogging a dead horse a little more.)

[JKent]

Personally I don’t treat the twelve point five surrounds 

[npt3]

🎉🎉🎉🎉🎉

[RoyC]

On 2/9/2022 at 8:06 PM, npt3 said:

So, I'm having a pause before treating my driver surrounds with Roy C's sealant.  Is there any downside to NOT doing it?  (I only ask because the driver I want to treat has a really nice, clean and translucent surround that does not appear to be degraded or damaged in any way.)

I recently worked on a KLH 21. The driver's suspension was quite worn and very porous, and there was some distortion at moderate volume levels. Normally I would not suggest using it, but in this case it seemed beneficial. If you have some available, it will not hurt its performance to brush some on the surround.

Roy