[tehsn1p3r]

Hello Headfi!
 
My Uncle and I have been hard at work on a Millett Hybrid Minimax for many months now, and we've finally got the board fully stuffed, but there's one major issue, there is no sound coming from it, and no sign of it either. Not even a little crackle when the headphones are plugged in. Nothing.
 
Now, we changed up a few things, like putting orange drop caps on the back of the board (so they'd fit). However, every reading checks out, strangely enough. The 12FK6 tubes light up just fine, the Power Supply voltage checks out, the DB and Tubes are biased just fine, and literally everything checks out, there is just no sound. The RCA jacks are consistent, too.
 
Is there anyone out there who had a similar issue? Any idea as to what could be going wrong? Any help would be appreciated.

 

[FallenAngel]

1) Check that output resistors are populated or jumpered.
2) Check DC voltage before the epsilon circuit.

 

[tomb]

Ditto what FallenAngel said.  If all the readings are correct, but you get no sound, the suspect is the relay-delay circuit.  (I try to refrain from calling it "Epsilon," since it bears little resemblence to AMB's circuit anymore.  In the MOSFET-MAX's updated delay circuit, for instance, the only similarity you can claim is that it uses a relay.

)
 
Anyway, it's quite stable on the MiniMAX as it's used for a time-delay only.  From a cold start, that delay can take around 45 seconds, so you need to be sure to wait an adequate time before concluding that no sound is there.  If you can hear the relay click after about 45 seconds on a cold start (about 20-30 seconds from a "hot" start), then the relay is firing and the problem lies elsewhere.

 

[jdkJake]

Any pictures? As they say "a picture is worth a thousand words". In this case, it is really true.

Top and bottom, as much focus and light as you can manage.

 

[tehsn1p3r]

It turned out to be the switch. We jumped it, and now it works. Now I'm giving it 30 seconds before pumping any signal through it when I turn it on. This won't create any issues, will it?
 
Thanks for the help, and sorry to bump this thread.

 

[jdkJake]

I assume you mean the relay switch?

The worry is not signal into the amp, rather the potential for DC current to be passed on to your headphones during warm up if they are plugged in while power is applied.

I suggest you replace the part. In the meantime, do not plug your headphones into the amp until it has been on for about 45 seconds. Signal into the amp does not matter.

 

[tomb]

I agree with jdkjake, but you need to tell us what you mean by "switch."  Is that the relay or the power switch?  Have you jumped the relay?  If so, we need to figure out what's wrong.  I've never seen or heard of a bad relay in hundreds of MiniMAXes that have been built.  So, if that's what you jumped out, I suspect there's something else wrong with the relay-delay circuit.