Reduction Build Problem - Power Supply Fail

[burgerbassist]

Hey All,

This is my first post, so please be gentle.

I just built my second kit last night - a Reduction (a Quickie with PJCCS was my first, and it went well) - and I had thought it went smoothly.  When I finished the build, however, I plugged in the unit and only one tube lit up (the tube on the right once everything was put together) and the unit started smoking, so I immediately turned it off. I'm still in the process of fully inspecting, which will continue in an hour or so, but I took a picture of the damage. Can anyone here possibly help lead me in the right direction as to what went wrong? I've inspected everything near the burned resistors (see attached picture) and I've gone back through those particular instructions and I believe everything to be correct.

Thank you in advance.
- Dan

 

[Doc B]

The burnt resistors indicate that there is a short somewhere downstream from them in the circuit. Pictures of the tube sockets would be helpful.

 

[fullheadofnothing]

The resistors look wrong. Possibly the 18KΩ used where they should be 1KΩ...? Could you also post pictures of the other side of your power supply, where the diodes connect to the transformer?

 

[burgerbassist]

Thanks guys. I'll post more pics in a few. Are those resistors likely shot? If so, I'll need to source more and I'd like to get on that sooner than later.

 

[burgerbassist]

Hey All,

Sorry for the delay.  I got held up at work, then came home, inspected, and found that I had two unsoldered resistors (a 75K ohm between 14L and 15L, and a 75K ohm between 18L and 19L) near the tube sockets that were causing the excess heat in the power section.

So, I got it working, and the bass response was a little underwhelming, so I moved on to the Integration upgrade.  I got the shunt regulator installed, it was working, and I hooked it up to listen to while I worked on the two C4S boards.  I played probably 10 songs through it, and it suddenly started making a noise that sounded like when the needle skips across a record.  I unplugged and soldered in my C4S boards, thinking I'd rather troublshoot the whole thing at once, and now only like half of the LEDs light (3/4 on the shunt regulator, 2/4 on one C4S board, none on the other, and 3/4 in the tube sockets).

I also am only getting ~50 volts at terminals 2, 1 8, 26, and 31, rather than the 65-90 volts DC specified in the end of the Integration manual.

My question now is - could those resistors have burned out and caused the sound I heard after playing a few songs with the shunt regulator installed?

Pics have been uploaded of the tube sockets, the other side of the power section, the LEDs that are and aren't lit, and an overall pic of the assembled unit.

Thanks again!

 

[Paul Birkeland]

This probably isn't what you want to hear, but it would be a really good idea to take the Integration upgrade out and run your stock Reduction for a couple of weeks.  At this juncture, you could be having the same problem that you've had before (maybe a loose connection that was moved while effecting other repairs).  The two forward C4S boards can be pulled, the 18K plate loads put back in, and the middle C4S board can stay for this testing.

-PB

 

[Doc B]

Peebs beat me to the punch.

First you need to measure those resistors to see if they are still good. Disconnect one end of each one before measuring because the meter will charge the capacitors they are connected to and muck up the reading. Once you verify whether they read the proper resistance value, you need to go over the preamp and reflow all of the solder joints. That might fix the weak bass if you have a bad connection in the EQ that is bad, and may fix your new problems unless they are from miswiring the connections.

If reflowing the solder doesn't fix things you really should roll back to the basic circuit and get it working correctly as PB suggests. Then add the shunt regulator and get it working properly. Then add the C4s and get it working properly.

 

[burgerbassist]

Hey Guys,

Sounds good to me.  I will note that the bass was improved with the shunt regulator, which the manual said would be the case.  I do appreciate the assistance, though.  I'm new to all of this, so I don't have the theoretical knowledge behind me to figure all of this out on my own yet.

And if that's what needs to be done, it's what needs to be done.  I can live without the extra gain from the C4S cards for the time being.  I'd rather do this right than do it quickly.

I did pick up some 1w 1k ohm resistors from a nearby electronics store, but they are brown black red red instead of brown black red gold (2% tolerance vs 5% on the provided resistors, to my understanding).  Are these interchangeable if my current resistors are burned out?

- Dan

 

[Paul Birkeland]

The tolerance of those 1K resistors isn't critical.  10% parts would be OK in that position (not the case elsewhere in the circuit though!).

-PB