Little Paramount problem [solved]

[Jeroen]

Dear people,

Just finished a pair of Paramounts.

Amp A works well and sounds very good.

Amp B works, but hardly amplifies.

Some measurements that didn't correspond the checklist;

terminal strip 5  (217 V)                 Amp A=188 V    Amp B=50 V

4 pin socket  A3  (217 V)                Amp A=145V     Amp B=160 V
                    A2 (464 V)                Amp 438 V        Amp B=492 V

Soft start board  Kreg A  (4.1 V)    Amp A=2,9 V     Amp B=3,2 V
                         Kreg B  (6,3 V)    Amp A=7,3 V     Amp B=7,3 V

Does anyone has a suggestion what the problem could be with Amp B?
Does anyone knows if the difference in voltage in the Soft start board influence the sound?

Help is very appreciated!

Best Regards, Jeroen from the Netherlands

 

[Paul Birkeland]

Just to clarify, you built these as 2A3 amps?

Were you able to trim the OB voltage on either amp to perfection? (page 66)

Try trimming them out to see if you can hit your target, if you have run out of trimming rotation on that control, let us know.

-PB

(Welcome to the forum!)

[Jeroen]

Hi Paul,

Thank you for your quick responce.

The amps are with 2a3's.

I was able to trim both amps,  amp A; 438/3= 146 V, amp B; 492/3=164 V.

Like I mentioned, amp A works fine. The problem is that amp B hardly amplifies.
I checked all wires, resistors etc, everything is correct I think..

Regards,

Jeroen

[Paul Birkeland]

Can you triple check that you haven't switched the 2.49K resistors and 249K resistors? 

The 249K resistor is between 16 and 18, the 2.49K resistor is on the PC board next to the brown 0.1uf film capacitor.

If the 2.49K resistor is accidentally between 16 and 18, you'll lose a whole lot of output.

-PB

[Jeroen]

The resistors were in the correct place.

Any other suggestions what could cause the low output?


Jeroen

[Jeroen]

Just figured out the problem!

One of the Sovtek tubes with came with the kit doesn't work.

I think a order a new (pair) in Holland, otherwise I have to wait some time if it send from the US.

Do you recommend the Sovtek, Electric Harmonix or JJ tubes?

Jeroen

[Mike B]

I love my EH 2A3 golds -

[Jeroen]

Hi Mike,

Thanks for your reply!

Just ordered a pair of EH 2a3 24K gold , I'm very curies about their sound (stage).

Did you tried different tubes before playing with the EH?

Regards,

Jeroen

[Mike B]

Just the stock Sovtecs.

I tried some Full Music mesh plates after the 2A3 EH and put the EH golds back in.

They are very nice tubes and are not expensive.  Look good too with the nice porcelean bases.

I ordered up another pair for back up.