Power Supply/ New Build #183 clone

[CHIP]

Thanks Tom, Like you mentioned in one of your posts, there's a lot of work ( wiring and such) with these amps. I can see why pro builders charge around 3 grand for an amp of this caliber.

[Structo]

Yes, it is amazing how many connections there is in one of these amps.
Very labor intensive.

[CHIP]

I played the amp for about 2 min, (wife's home), but initial reaction was WOW. Amazing the difference from my tweaked d'lite, (which I do like).
Voltages are surprising , since I used a PT that J Borders recently offered fer sale, with 340v @450ma on the primary. Thought the power tubes would have been higher.
plates are;
V1a 176v
V1b 179V
V2a 186v
V2b 182v
v3a 280v
V3b 275v
v4 pin3 425v bias 30ma
v5 " "
v6 " "
v7 " "

[ToneMerc]

I played the amp for about 2 min, (wife's home), but initial reaction was WOW. Amazing the difference from my tweaked d'lite, (which I do like).
Voltages are surprising , since I used a PT that J Borders recently offered fer sale, with 340v @450ma on the primary. Thought the power tubes would have been higher.
plates are;
V1a 176v
V1b 179V
V2a 186v
V2b 182v
v3a 280v
V3b 275v
v4 pin3 425v bias 30ma
v5 " "
v6 " "
v7 " "

Chip, what were the unloaded V4 && V7 voltages?

TM

[CHIP]

TM,
450v unloaded.

[Structo]

That does seem to be low on the power tubes.

My Magnetic Component PT gives me 433 on the plates.

I thought Jason's PT was higher voltage than that?

What is your wall voltage as your preamp voltages are also low?

What choke did you use and what screen resistors?

[ToneMerc]

TM,
450v unloaded.

Chip, that's way low, whats your line side voltage? At 123V, the 345V Twin PT that I spec from Heyboer comes in around 490+V unloaded. The 340V one, around 480 or so. However, my HT current spec is higher and a .5A heavier on the filaments.

I need to check the one that I ordered from J.

TM

[ToneMerc]

FYI, awhile back I asked Jason what secondaries voltages he's seen on his power transformers.

"The HV secondary on the couple I have are between 341VAC - 344VAC (682V - 688V) @ 120V regulated AC"


TM

[CHIP]

this morning I fired the amp up with 119.5 v line voltage and my tube plates are coming in at 435v DC. (That's a little better)
My line voltage must have been lower last night , I think I did see it coming in at 118v last night.

[CHIP]

I guess if my line voltage was 123v I'd be right on target.

[Structo]

What primary voltage is the PT spec'd at?

[ToneMerc]

What primary voltage is the PT spec'd at?

[CHIP]

That does seem to be low on the power tubes.

My Magnetic Component PT gives me 433 on the plates.

I thought Jason's PT was higher voltage than that?

What is your wall voltage as your preamp voltages are also low?

What choke did you use and what screen resistors?

Twin choke from mercury mag.
1k5 screen resistors

the PT is right on actually, i'm getting 340vac on the secondary at 120v line voltage.

[ToneMerc]

I guess if my line voltage was 123v I'd be right on target.

I still think it's a tad low. If we split the HT differences of what Jason has seen that would be 342.5V@120VAC

342.5V * 1.41 = 482.9V unloaded

Using my load junk math figures, it should have about 455.5V loaded/120VAC

The difference between 120 & 123VAC on the PT secondary is around 8V. Thus, this same PT at 120VAC would be equal to a 350.5VAC sec @123VAC.

350.5 * 1.41 = 494.2V unloaded

Using my junk math load figures, it should have about 466.2V loaded/123VAC


TM

[CHIP]

I guess if my line voltage was 123v I'd be right on target.

I still think it's a tad low. If we split the HT differences of what Jason has seen that would be 342.5V@120VAC

342.5V * 1.41 = 482.9V unloaded

Using my load junk math figures, it should have about 455.5V loaded/120VAC

The difference between 120 & 123VAC on the PT secondary is around 8V. Thus, this same PT at 120VAC would be equal to a 350.5VAC sec @123VAC.

350.5 * 1.41 = 494.2V unloaded

Using my junk math load figures, it should have about 466.2V loaded/123VAC


TM

Yeah I'm about 15vdc low . What could cause this?