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Hey guys,

I´m awaiting my speaker today, so I finished up the amp yesterday evening. Checked all connections triple, and then started testing voltages this morning.

I think I have a problem though:

First I checked the voltages on the rectifier and heaters (without the rectifier installed):

(I have 228 V coming out of the wallmart)

Rectifier pin 6 and 4: 345 V
Heaters (all): 5,9V

I thought that´s close enough, so I installed the 5Y3GT and powered up again:

DISASTER !!!
First the rectifier had a nice little glow. Then just as I was getting ready to test voltages on V3 and V4, the VRM FET crapped out.

It gave a nice fireworks show ( and a scorchmark on the chasis) It smelled nice though....

Then the 5Y3GT started glowing ever more brightly. I was afraid it might blow up, and take the city along with it.

I put it on standby and powered off. After that I tried to power up once more, but noticed that the rectifier now has no glow whatsoever.

Do you think it´s just the FET, or also the rectifier tube that´s toasted ?

Is it wise to try and bypass the VRM, and see if the rectifier is still ok, or try it with a new rectifier while bypassing the VRM ?

Anyone has any suggestions on how to proceed from here ?

Thanks,

UPDATE:

I just bypassed the VRM, and checked the rectifier again....

0 V going out....damn !

I just ordered a new 5y3gt, guess I´ll have to wait until tomorrow to finally play my Tweed

I was going to suggest starting with a stock build but you seem to be doing that. Good luck.

Yes, best to get an amp working first, then add the modification. Check AC Voltages before inserting rectifier, and all wires leading to hi voltage power B+.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Thanks guys.

I checked the AC voltages before I inserted the rectifier
I have 228 V AC coming out of the wall.
Then 345-349 V on pin 6 and 4 of the rectifier.
As I said, the heaters all checked out. (5,9 V)

I noticed the 345-349 V AC is somewhat lower than mentioned in the manual. Does this depend on wether you have 120 V or 220 V going in ?

I can´t think of any other reason why the voltage on pin 4 and 6 could differ. I mean 220 straight into the PT and then from the PT straight to pin 4 and 6....would could go wrong there ?

I´ll have a new rectifier tomorrow, so stay tuned for the second round. Personally I think the VRM is the culprit. Perhaps I put in the FET the wrong way around..... Could that result in cooking it ?

Is the IRFPE50 the only FET you can use ? I´m having a hard time finding a distributor for it here.

The PT wont be perfectly balanced on the two leads so you'll get a small difference. You will also get lower voltages with 230 as the PT is for 240. But that's a good thing to get a Tweed sound.



Yes, reverse the leads is not a good thing and also, did you insulate the FET from the chasis with the mica washers & white heatsink compound? Just trace all the connecting wires to the leads and be sure to ground yourself before touching the FET. Get the amp going first. New FET is already in the mail for you!

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Wow Stephen, you´re customer support keeps amazing me ! I also received notice about the chasis. My next kit will certainly come from you....now only to decide which one (and save up a little).

I used one mica washer between the FET and the chasis, and a little heatsink-compound between the washer and the chasis as well as between the washer and the FET. I checked that the leads from the FET weren´t touching the chasis. (measured resistance between leads and chasis)

My guess is it will fire up fine tomorrow, just not with the VRM. Bad luck for the neigbours !

Thanks again.

Thanks, Check the orientation of the zener as well.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Hi guys,

I just powered up my Deluxe again.
This time with a new 5Y3GT (TAD) and bypassing the VRM.
It seems all is ok.

I have the following voltages with all tubes installed:

AC Mains: 228 V
B+ No tubes installed: 482 (319 on standby)
B+ All tubes installed: 397

Rectifier

pin 4: 345
pin 6: 345

V1
pin 1: 127
pin 2: -
pin 3: 2,1
pin 4: -
pin 5: -
pin 6: 127
pin 7: -
pin 8: 2,1
pin 9: -

V2
pin 1: 165
pin 2: -
pin 3: 1,2
pin 4: -
pin 5: -
pin 6: 199 (this wonders me a bit...should be 175)
pin 7: -
pin 8: 50 (this wonders me as well...should be 70,5)
pin 9: -

V3
pin 1: -
pin 2: -
pin 3: 390
pin 4: 356
pin 5: -
pin 6: -
pin 7: -
pin 8: 21

V4 exactly the same as V3 (+/- 1 or 2 V)

Should I be worried about pins 6 and 8 of V2 ?

It sound great though !

I couldn´t really turn it up, my baby girl is already sleeping....and the VRM is inop...

The amp is really quit. Sounds great, no percievable hum or anything. I did notice that bringing up the unused volume introduces quite some noise when above 5 or 6. Is that normal ?

Tomorrow I wil put it through the test and really check it out, but I´m already loving it !!

I would appreciate it if someone would take the time and check if my voltages are ok.

Thanks,

The voltages look to be in the ballpark. Different tubes will behave differently and result in different voltages.

Turning up the vol pot on unused channel should not add a lot of extra noise so maybe check the inputs are grounding properly when there is no input in that channel.

Sounds like you are on your way though!

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Thanks Stephen,

the input grounding might well be the problem. I had some trouble getting those done. I used shielded cable directly to the resistors on the pins, but getting the shields neatly on the ground connections of the inputs proved difficult because the shield was so thick.

I think it looks messy, and am planning to do those from scratch again when the new chasis gets here. For now I´ll check them and see what I can do.