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Tubelab Discussion and support of Tubelab products, prototypes and experiments

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Old 24th April 2018, 12:02 AM   #11
PDL is offline PDL  United States
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Join Date: Jan 2010
Location: Minneapolis
Originally Posted by JonSnell Electronic View Post
This forum is for the DIY enthusiast called diyAudio and covers most topics, not restricted to valve issues.
Without knowledge of the tank capacitance value used; {no more than 60uF see https://www.radiomuseum.org/tubes/tube_5ar4.html}, any higher value would definitely cause problems and be totally inappropriate. The capacitor shown looks to be a higher value.
I have been designing, building and selling valve HiFi amplifiers, professionally for many years.
The first thing one learns at an early stage is if you wish to change a reputable design, there are rules of safety and then the suitability of a component for a specific job and fitting motor start capacitors to a DC power supply is asking for trouble because valve rectifiers like a slow load build up, the Anode series resistance is between 160 and 200 Ohms, not a sharp current rush (from a low ESR capacitor), otherwise the rectifier destroys itself.
Valves were designed in the days of paper capacitors with a high ESR.
I hope that clarifies a few points.

So to sum up, safety is paramount, component type and fitting, design and suitability is next followed by a host of other issues.
If you think that the wrong type of capacitor is better than the correct type, be my guest.
I await the acid remarks.

His motor RUN capacitor of 100uF is perfectly acceptable as it's not the INPUT cap and and it's essentially a big poly cap.

If you want to help people on THIS forum, the TUBELAB forum, specifically NOT the tubes/valves forum, please study the schematic. The PSU is a very simple and a standard CLC type.

Also, this amp has been fitted with thermistors to help further reduce inrush/startup current.

Wait ten minutes for the thermistors to cool down before restarting after turning turning the amp off.

The first thing one learns when troubleshooting is to be humble and re-read all suggestions.
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Old 24th April 2018, 01:50 PM   #12
johnzm is offline johnzm  United States
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Join Date: Jul 2010
Originally Posted by juststeve View Post
the yellow and brown wires coming from your transformer I have those swapped as per reading on this site. I have the XPWR059
Running fine with no issue


Click the image to open in full size.

Click the image to open in full size.

Wiring Diagrams | Tubelab

The green wires are the 6.3 volt filament wires. They are connected to the T1-grn terminals.

Click the image to open in full size.

looks like just our transformers use different colors for the 5 volt and 6.3 volt taps
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Old 24th April 2018, 03:14 PM   #13
Tubelab_com is offline Tubelab_com  United States
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Location: West Virginia panhandle
the yellow and brown wires coming from your transformer I have those swapped as per reading on this site.
Edcor makes good transformers. They however defy the nearly hundred year old standard for transformer wire color.

Today we have EIA (Electronics Industry Association), it evolved from RETMA (Radio, Electronics, and Television Manufacturers Association) which came from the old RMA (Radio Manufacturers Association) Their standard is in the link, and has been convention for a long time.


From the two spec sheets posted above, they also change them at will amongst their own transformers. This guarantees confusion with DIY amp builders. As stated the 6.3 volt wires which are green by the standards should go to the terminals on the rear of the board, and the 5 volt wires, usually yellow, go to the side of the board. Getting these wrong will probably make the amp play, but reduce the life of the tubes......a lot.

Primary leads -------------- black
(if tapped)
Common ----------------- black
Tap -------------------- black/yellow
End -------------------- black/red

High voltage secondary ----- red
Center tap ------------- red/yellow

Rectifier filament winding - yellow
Center tap ------------- yellow/blue

Filament winding No. 1 ----- green
Center tap ------------- green/yellow

Filament winding No. 2 ----- brown
Center tap ------------- brown/yellow

Filament winding No. 3 ----- slate
Center tap ------------- slate/yellow
Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before......
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Old 25th April 2018, 05:24 PM   #14
johnzm is offline johnzm  United States
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we got a bit off tangent here. did i purchase the wrong style fuse for mine?
is that all i need to make it a reliable beast again?

and whats currently the best rectifier tube to pickup?
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Old 3rd June 2018, 11:32 PM   #15
johnzm is offline johnzm  United States
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well guys,

i i ended up with some fuses with the little solder blob in the middle of the wire, and it still pops them.

i had a buddy borrowing the amp, and he called me one night saying it stunk and a part fell off.

he said he kept playing even after the part fell, but (the capacitor) is useless bulged and the wrapping rippled up from the heat.

see the attached pictures, what do you think caused this? also the burn mark on the board i cannot figure out why unless the resistor was dumping heat, but it should have had plenty of room to vent that heat out?

i included a pic from the same part of the circuit from the other side as welll, i dont see any issues on that side. maybe a bad tube?
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File Type: jpg 20180603_182519.jpg (665.5 KB, 42 views)
File Type: jpg 20180603_182530.jpg (623.0 KB, 34 views)
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