Hi all,
I am doing a favour for a neighbour who had an unrestored Kriesler 11-88 as his only record player. It had one channel not working and the (varnish?) finish was falling off.
After pulling it apart, both speakers were moth-eaten, and I have repaired those with glue and tissue paper. Next one output transformer was open circuit, obtained a replacement and after getting the primary around the wrong way initially, it now has both channels working. 3 coats of varnish and it is looking semi-reasonable. The turntable needed new rubber motor mounts, had a seized cam bearing and of course solid grease. It now all functions very well. The crystal cartridge also seems (at this point) to be ok. Replaced all the electrolytics and the rectifier as B+ was 100 volts low. Voltages now measure spot on, although I haven't measured the 75V on the 12AX7 plate. Replaced all the resistors as they were all over the place, a couple open circuit and values way over tolerance. Changed the power cord and fed proper 3 pin cable to the turntable with a proper earth.

Adjusting the balance, tone and volume was an exercise in patience to find a spot where you actually got sound out both channels, so I obtained replacement 1M dual pots (but couldn't find an audio taper for volume and a switch on the tone). That fixed the tone, but the volume is even worse than ever and the balance is all one way. The other way there is output, but it is very muffled and low and the other channel still comes through. It was recommended to measure for DC on the pots, which there doesn't seem to be.

I have ordered a 12AX7 guessing that is the low channel issue, could it also be the crackle when you adjust the volume? I have also ordered a couple of 0.0022μF to replace C13 and C14. I think I have 0.047 for C15 and C16 as well.

Any other ideas on the nasty crackle? Surely the new pots wouldn't be that bad. I guess I need to get it back on the bench and feed tone into both channels to see exactly how different they are.

https://www.kevinchant.com/uploads/7/1/0/8/7108231/11-88.pdf

Thanks,
Glenn.

I guess I need to get it back on the bench and feed tone into both channels to see exactly how different they are.

That is how I would proceed, after verifying all voltages. Compare one channel against the other along the audio chain. Also, look for cold/dry solder joints.

Crackling when adjusting a new pot is almost certainly due to DC flowing through the control. Replace C13/14/15/16. If it still crackles after that, but only on the radio position, replace C9.

I'd also replace C17,18,21,22 because it's certain the old ones are leaky. Not sure if you checked R17/18/19/20, but it's important that you do. Also R30 and C23.

Once you've got the sound working, you should also replace C1.

110v on pin 6 and 85 on pin 1 of the 12ax7, so I am going with low emission on one side in particular. Replaced C15 and C16 and maybe the crackling is a little better. Hopefully 12ax7 and caps will arrive tomorrow.
Will update after swapping them out.

Are the caps paper or poly?
I see the cct has the date at 1961 so it would be on the cusp of using poly caps (philips mustard caps?).
If they are paper change the lot.
Also hit all the pots and switches with Deoxit spray (available from Mektronics). It's the best contact spray by far.

The caps are mustard caps.From what I have read they tend to be ok. That aside, I have replaced all except C19 and C20, which are mica and apparently Aussie versions of those don't tend to be troublesome. I have replaced all resistors and all caps on the audio side except the two mica's. The crackling still persisted, so I dosed the pot with Electrolube and after 30 odd twists, most of the noise has gone. I can only conclude that the pots are NOS and haven't been stored properly.
I also replaced the 12AX7 and that sorted the low channel and imbalanced voltages.
The balance control is not very good, but maybe that is the way it was in this design anyway.

Overall, it now plays a record as well as I can imagine this primitive design can do.

Thanks everybody.

Hi Trackhappy,

This might be worth reading. Quote taken from :https://www.justradios.com/captips.html

"Hello Dave,
The text was as follows:
"When restoring a valve radio treat all Mica capacitors that are connected to high voltages, such as between anodes and earth, as potential faults and replace them with a new mica component from the AVRS component store".
Many of the 'Simplex' brand Australian made Mica capacitors from the 1940's and 50's suffer from silver migration through the mica and it appears that this is due to porosity in the mica used at the time. If the outside moulding is damaged or lets moisture through then the failure is accelerated. When the silver finds its way through the mica, small 'whiskers' from either side make contact and can be blown away, (if sufficient voltage or current is available), resulting in intermittent crackling noises and other faults if high voltage finds its way into places where it should not be.
The failure mode only occurs when one side of the capacitor is connected to a high voltage and the other to a low potential point or ground.
As a general rule they need to be treated with suspicion and, to be on the safe side, replaced.
I have heard some restorers from the US say that "I have never changed a Mica in my life" and, while this may be an exaggeration, I have found that quite old US made mica caps do not seem to suffer from the same problems as our own ones. Maybe they used a different grade of mica in their construction.
The dipped types that we purchase from you do not cause any problems.
Regards,
Warwick
Nov. 2014"



"After reading the above the mystery was solved. I had noticed that overseas customers were mush more likely to order mica capacitors than American customers. The need to replace a mica capacitors must depend on the quality of the original mica capacitor. Tube radios made in the USA and Canada which used high quality mica capacitors rarely go bad whereas the mica capacitors used in Australian, UK and other overseas radios must have been "not so great" these radios are much more likely to have mica capacitors in need of replacement. "

The mica problem (if there is a problem) with C19 and C20 will happen regardless of the settings of the controls, even with the volume right down. If there's crackles without you touching anything, only then start thinking about replacement.

I've found that any Aus made caps are prone to failure.
I've seen the AEE brand film caps burst into flames before my eyes.

AEE unwisely marketed their "printed circuit" caps for mains filter applications. They were not suitable. When used in low power circuits they are OK. AEE plastic film caps (usually yellow) are also OK.

AEE also made high current, high voltage caps that were used in many solid state B&W TVs across the hor. OP transistor. These work very hard and can catch fire or fail S/C. Usually the transistor is unaffected but you must use a suitable (read "large, high current") cap to replace it.

Otherwise (and this from more years in the service industry than I care to remember) Oz cap makers were no better or worse than other countries' efforts. UK, US, Germany, Japan made paper caps all fail. A paper or mica cap will by now be bad no matter where it comes from, although as stated a mica connected across a coil will still be OK.

Polyester caps (including Philips "mustard" caps and blue or green Ducons) do not ever need to be replaced unless they have been obviously damaged by some other failure. White UCC "Dipol"s are OK, UCC "HiQual"s are paper and are not OK.

In early colour sets watch out for pink tubular "mixed dielectric" caps. These were used in high power deflection circuits. They look like plastic caps but are actually paper and oil. They will be leaky by now and can catch fire.

Clear plastic tubular styrene ("styroseal") caps can go intermittent O/C especially in oscillator circuits, causing the oscillator not to start when cold. If suspected they must be replaced with a similar part - most plastic caps have a temperature co-efficient and will cause the oscillator to drift with heat, Styros do not suffer from this problem.