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PostPosted: Sat Feb 13, 2021 11:22 pm 
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On the good side:

Jewel lights up bright, no smoke, bulb limiter bulb does not light up.

With my dmm set to a/c and the common lead grounded to the chassis, I’m getting 3.3 on each side of the lamp lugs and tube filaments. 6.7 across them.

I’m getting -42 d/c at the bias pot wiper.

Pab and od Relay switch fine with the foot switch.

Nothing seems hot.

Now for the bad stuff:

With dmm set to dc and grounded to the chassis, B+1, 2, and3 only charge to about 135 after a couple minutes. B4, 5 are about 116 after that same period.

Do I have to wait longer? No tubes or load yet.

I checked the d/c side the rectifiers where they come together around the same time and it was in the low 300’s d/c I think maybe 315 or so.

Ideas?


Last edited by JerryDT on Sat Feb 13, 2021 11:39 pm, edited 2 times in total.

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PostPosted: Sat Feb 13, 2021 11:28 pm 
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Also, my primaries are getting about 335v a/c each with respect to ground


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PostPosted: Sat Feb 13, 2021 11:34 pm 
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All measurements above taken with bulb limiter... if that makes a difference. And with the stand by switch off. I went ahead and reflowed the rectifiers and caps, but it made no difference.


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PostPosted: Sun Feb 14, 2021 10:32 am 
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Remove the limiter!! See if that fixes it.

Disconnect the hi v secondaries and measure the AC voltage. is it to spec or close?
Check the orientation of the power supply diodes.

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PostPosted: Mon Feb 15, 2021 12:08 pm 
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coco wrote:
Remove the limiter!! See if that fixes it.

Disconnect the hi v secondaries and measure the AC voltage. is it to spec or close?
Check the orientation of the power supply diodes.


I tried all of this. Removing the limiter made very little difference. I disconnected the hi v secondaries, and they measured 335vac per lead with respect to ground.

Diodes all have the stripe facing away from the ac leads.

Could I have a bad rectifier? Or maybe a bad 100m cap?

I also measured the far side (where the diodes come together and got 315dc with the limiter in place.
https://rexdon-my.sharepoint.com/:i:/p/ ... Q?e=1bpfrg


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PostPosted: Tue Feb 16, 2021 3:27 am 
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The picture you shared looks like the main eyelet board isn't supported on stand-offs, which drastically increases the chances of a short! Can you confirm that it's mounted securely and safely?

Also not shown in the photo are the two HV wires connected to the diodes. It would be good to know that both wires are connected correctly to their respective diodes.


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PostPosted: Tue Feb 16, 2021 9:29 am 
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bushwhacka wrote:
The picture you shared looks like the main eyelet board isn't supported on stand-offs, which drastically increases the chances of a short! Can you confirm that it's mounted securely and safely?

Also not shown in the photo are the two HV wires connected to the diodes. It would be good to know that both wires are connected correctly to their respective diodes.


Thanks for trying to help! I had temporarily disconnected the hv leads to double check voltage. However, my issue was actually simple ignorance that would have been easily fixed by a good look at the schematic, which is normally over my head but in this case, understandable. I had not been switching the standby on, nor had I plugged in a load. The load was probably not necessary yet since I didn’t have tubes installed yet, but the standby obviously was necessary.

Played till after midnight! Love the app after just one night.

I


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PostPosted: Tue Feb 16, 2021 12:42 pm 
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JerryDT wrote:
bushwhacka wrote:
I had not been switching the standby on, nor had I plugged in a load. The load was probably not necessary yet since I didn’t have tubes installed yet, but the standby obviously was necessary.


Brilliant!

Just in case you don't already know: the amp should never be played without a load connected (speaker / dummy load) because it can fry the output transformer.

Glad it's sorted :)


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PostPosted: Tue Feb 16, 2021 1:05 pm 
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bushwhacka wrote:
JerryDT wrote:
bushwhacka wrote:
I had not been switching the standby on, nor had I plugged in a load. The load was probably not necessary yet since I didn’t have tubes installed yet, but the standby obviously was necessary.


Brilliant!

Just in case you don't already know: the amp should never be played without a load connected (speaker / dummy load) because it can fry the output transformer.

Glad it's sorted :)


I think it was a case of me still very much learning, and trying to follow the builder's guide to a "T"... it's one of those details many may take for granted, but I just learned. Looking back, I understand now from the schematic that when the standby switch is off, the only dc being passed to the B+ was what was bleeding through the 220k resistor. Finally, the mystery of the standby switch has been revealed to me. Lol


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