Bottlehead Forum
Bottlehead Kits => Kaiju Stereo 300B amp => Topic started by: joralieu on April 19, 2024, 12:46:58 PM
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Driver testing I have 513 on 1A and 152 on OA also the LEDs on the B side are both out. It's the same for the A and D socket. Where do I look first.
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I would post some photos of your build so far. The 152V at OA could be related to the zener diode installation on the 5 lug terminal strips behind the 9 pin sockets, but I would bet on a missing jumper or a jumper going somewhere it shouldn't be on the PC board itself.
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Here are some photos
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It would likely be best to remove one of the boards, flip it over, and show a picture of the bottom as well.
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Another thought, I had my LM431A's in backwards. I desolderd them and turned them. Could that be the problem?
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Also had the JC29 backwards, had desolder and resolder them. Wonder if I may have damaged something in the process
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Did you swap the PN2907 with the 431, or did you install them all backwards? If you put them in backwards and powered up the amp, then you will need to replace all of those parts.
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They were all in the right place but I had the flat sides facing the wrong way. I corrected that before It was powered up.
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What are you Kreg voltages?
Even if not powered up, reworking these boards can be tough. Still, you have the exact same problem on both boards, so the same error is likely present on both sides.
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Socket A Socket D
Kreg A 4.1. Kreg A .06
Kreg B 1.8. Kreg B 1.8
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Both B side Kreg voltage indicate saturation, which would make me very, very interested in seeing the bottom of each C4S PC board. I would wonder if there are solder bridges present between pins on some of the transistors that got swapped around.
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Here is the bottom side.
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Could you double check that you have the 2.49K and 249K resistors in the correct places.
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That's It, those are in the wrong places. Would powering that way damage anything?
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It's quite possible that the 431 regulators may need to be replaced on that side of the board, but you can power it up and see.
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Ok I have the resistors in the right spots now here is what I got.
A socket. D socket
1a 519 1a 519
Oa 298. Oa 349
All the led's light up
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OK, well the side with 298V is likely working properly. What are the Kreg voltages on the side with 349V at OA? Does the 5670 glow on that side of the amp?
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The 5670 on that side lights up Kreg A 3.75V Kreg B is 15V
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Any further advice?
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You had said before that both sides light up...
On the side with the OA at 349V, can you report both Kreg voltages on that side?
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Kreg A 3.75V
Kreg B 15V
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Those voltages suggest that that C4S board should be working, so I'd be looking for missing jumpers or a broken wire that's not allowing the regulator to pull things down properly.
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Kreg b on the right channel is 7V kreg b on the left channel is 15V, is this right?
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What OB voltages do you see on each side?
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A side OB 174V
D side OB 176V
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7V is the correct value. 15V means that you have a bunch of current being sucked down somewhere else.
On the 9 pin socket on the side with 15V, there is a little resistor that connects to the earth lug on the 5 pin terminal strip holding all the zener diodes. What is the DC resistance between the star ground screw in the center of the chassis and that terminal where that resistor connects? This connection not being 100% would prevent the 5670 regulator half from doing its job properly.
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I get O ohms there
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Would a bad 431 regulator on that side cause this?
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I've never seen a 431 fail in the way you're describing. I suspect a broken wire or missing jumper on the C4S board.
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CS4 jumpers look good to me and don't see any obvious miswires or broken wires, checked them for continuity. Any clues where else I could look? It is probably something simple , just not finding it.
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There's a terminal labeled "X" on the PC board, can you measure the DC voltage on that pad on the side where you have 15V at Kreg? Also it wouldn't hurt to just swap the 5670 tubes to be extra sure this isn't something that's tube related, though that seems quite unlikely under these circumstances.
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I get 2.9V at X I have swapped the tubes and it made no difference
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Fundamentally this may have a lot to do with the 2.49K and 249K resistor swap. You could try replacing the 431 regulator there, and that might work, but you may also just have an iffy joint or a lifted trace on one end of the 2.49K resistor on that side of the board. I would probably pop in a new regulator and add a little heat and solder to the 2.49K resistor.
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I reheated the 2.49k resistor and everything measures right now. Sheesh I knew it was something simple.
Thanks
Joe
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Ok, I finally got the hooked up and still have a problem. The left channel is significantly lower output than the right with the trimpots turned all the way up. Would this be a problem with the driver board? I have switched tubes and cables around and the left side remains low.
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Are the DC voltages consistent between channels? Most of the time when we see something like this, it's an issue with output transformer wiring if everything else is equal between channels.
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They were but maybe something may have happened since. I will check again which ones should check first?
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You can post some build photos, concentrating on the areas around the output transformers.
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All is good now. I had the black wire on the left side output transformer soldered to terminal 1 should be 3.
Thank you