Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Paramount => Topic started by: Kris on November 01, 2015, 05:45:49 AM

Title: Paramounts 2A3 resistances a little off [resolved]
Post by: Kris on November 01, 2015, 05:45:49 AM

Hi,
I just finished building my Paramounts and these two resistances are off:

Nine pin socket          reading           manual
           B2                       10.2k                8.2k
           B9                        0                         *

Both of my Patamounts have the same resistances.
All other resistances checked out within specs.
Not sure if I can proceed to voltage check.

Thanks,
Kris

Title: Re: Paramounts 2A3 resistances a little off
Post by: Paul Birkeland on November 01, 2015, 06:15:59 AM

Quote from: Kris on November 01, 2015, 05:45:49 AM

           B9                        0                         *

What do you get on B1?

B1 and B9 are fed by the 6.3V winding, which has a center tap.  The bare shield wire in the STP grounds the center of this winding, so you should have low resistance to ground at B1 and B9.

If B1 shows low resistance, then your wire either at the B9 or transformer end is not well connected (or there's a solder joint issue from the board to the transformer).

If B1 shows high resistance, then perhaps the bare drain wire is not well earthed.

Title: Re: Paramounts 2A3 resistances a little off
Post by: Kris on November 01, 2015, 06:59:02 AM

Thanks for your response Paul.
Judging by other readings that are indicated as * in my manual and they are in kilo or mega ohms range per my measurements, I was expecting * to be more than 1 ohm.
Well, manual version that I have is dated 07/23/2013 and it shows 0 on B1 and * on B9.
I carefully remeasured both pins and  I got 0.8 ohm on B1 and the same 0.8 ohm on B9, which is really close to zero on my meter, so I figured this as zero at first.
Again, both amps have the same measurements on B1 and B9.

When I touch probes together, my meter shows 0.3 ohm.

Please let me know what you think as I'm a little confused here.

Thanks,
Kris

Title: Re: Paramounts 2A3 resistances a little off
Post by: Paul Birkeland on November 01, 2015, 10:44:12 AM

I think you're OK, the * at B9 is a typo.

Title: Re: Paramounts 2A3 resistances a little off
Post by: Kris on November 01, 2015, 12:54:58 PM

Thanks again Paul.
I'll go ahead then and proceed to voltage check, assuming that 10.2k ohm on B2 (which is 25% more than specified in manual) is ok also. Am I correct?

Title: Re: Paramounts 2A3 resistances a little off
Post by: Paul Birkeland on November 01, 2015, 01:04:09 PM

If you adjust the little blue trim pot, the B2 value will wander around a bit, and the regulator's presence may change the reading also.  You're far enough away from 0 Ohms that there's no concern here.

-PB

Title: Re: Paramounts 2A3 resistances a little off
Post by: Kris on November 02, 2015, 02:29:37 AM

PB,
One more question...
I went ahead and did the voltage check. Everything looks good besides these: Kreg A is 3.2v for both amps (manual states 4.1v here) and Kreg B on one amp is 9.2v vs. 6.3 per manual. Kreg B on the other amp is within 15% tolerance though.
Is it OK to connect speakers?

Kris

Title: Re: Paramounts 2A3 resistances a little off
Post by: Paul Birkeland on November 02, 2015, 06:42:58 AM

Kreg A and Kreg B will wander a little bit.  Kreg A is actually adjustable, and when you adjust the blue trim pot to dial in the tube's plate voltage, Kreg A's voltage will be adjusted to do so.

Kreg B  just needs to be a bit above 2.5V, and well below 30V, so I'd say you're in good shape!

-PB

Title: Re: Paramounts 2A3 resistances a little off
Post by: Kris on November 02, 2015, 07:13:11 AM

Great!!!  Thank you PB for your help/clarifications.

Kris

Title: Re: Paramounts 2A3 resistances a little off
Post by: kip.duff on December 03, 2015, 04:19:38 PM

We're in the same boat.  At B2 I also got 10.2k Ohms for both amps.  KregA: 3.5V both.  KregB: 7.2 and 6.9V.

On B9 resistance, I was worried also- thought there was internal short from soldering iron burn in the STP wire between PT and B1/B9.  Disconnected filament output wires at PT and measured resistance across PT AC filament +, -, and neutral outputs: same reading at 0 to 0.2 Ohms- so I knew I was OK.