Troubleshooting Silvertone 1335 / Danelectro Challenger

[dirtgeek]

So I have this Silvertone 1335 amp that I've been working on, I completely recapped it and changed out most of the resistors as well, removed the death cap and changed to a 3-prong power cord. It had been sitting for years before I got it, so I hadn't even tried turning it on before I did all that work. Well now it seems like there's a short somewhere that I just can't find. When I turn it on, my limiter lights up and there's only ~103VAC going in. I've gone through and removed and replaced tubes, and found that the short doesn't happen when I pull either one of the 12AX7's, nor does it happen after I disconnect the phono cable from the upper chassis either.

This is my first time doing something this extensive, and I'm not entirely sure where to go from here. I've got a couple of tube sockets for the 12AX7's on order, in case that's the problem, but I'd like to see if I could get some input from more knowledgable and experienced brains than mine about this, and hopefully make a little more progress.

I also just learned that the Silvertone 1335 and the Danelectro Challenger Series D Model 89 are very similar, although the Danelectro is on it's side compared to the Silvertone. Thought that was interesting.

I've attached a link to the schematic, in case anyone might be able to help. Thanks!

https://el34world.com/charts/Schematics/files/Silvertone/Silvertone_1335.pdf

 

[gadget73]

What size bulb are you using for the limiter? If you're getting 103vac at the power cord, that honestly doesn't sound like any major problem with the amp. if there was a short you'd have much less voltage.

The 12ax7 are used as a cathode resistor. Pulling them will make the output stage stop conducting current, and thats probably going to be the largest current draw in the amp

 

[dirtgeek]

What size bulb are you using for the limiter? If you're getting 103vac at the power cord, that honestly doesn't sound like any major problem with the amp. if there was a short you'd have much less voltage.

The 12ax7 are used as a cathode resistor. Pulling them will make the output stage stop conducting current, and thats probably going to be the largest current draw in the amp

It's a 300w bulb. My variac is set at 117V, as that is what's specified on the schematic. When I pull the 12AX7, there is both 117V in the amp and 117V at the limiter. With the 12AX7 connected, both are reduced to 103V. The 12AX7s never light up or get warm regardless.

 

[gadget73]

Looks like they specify 19v across two of them, so you're under 10v per tube. At reduced input voltage you're going to see even less so it very well may not be visible. What does it do if you give it full power without the bulb? Make sure the fuse is the right value but I suspect it will run.

 

[cademan]

^^ What he said!

 

[dirtgeek]

Y'all are completely right! It totally works, what a relief. Thanks! I might need to replace a jack or two, and there's a little thumping coming from the tremolo (maybe the tube?), but otherwise seems to check out fine. That's been a long time coming, and a lot of learning. Thanks so much.

 

[baconbadge]

Y'all are completely right! It totally works, what a relief. Thanks! I might need to replace a jack or two, and there's a little thumping coming from the tremolo (maybe the tube?), but otherwise seems to check out fine. That's been a long time coming, and a lot of learning. Thanks so much.

If by "thumping" you mean you can still hear the tremolo quietly in the background even when it's turned down, that's normal. All my Silvertones do that. You can make a 1/4" jack to plug in the footswitch intput to short out the tremolo... just solder the sleeve to the tip.