Check the power supply voltage by measuring DC voltage between the chassis plate

Colman · 132

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Offline Colman

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Hello, I am on page 25 of the Moreplay Upgrade manual. I am confused by the instruction "Check the power supply voltage by measuring DC voltage between the chassis plate and terminal 21." One of my test meter leads goes to terminal 21. Where do I clip the other?



Offline Paul Birkeland

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Any metal on or touching the chassis plate. Any of the RCA jack ground tabs, any of the center lugs of any of the terminal strips, the IEC power entry module earth lug, stuff like that.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline AG

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Hello, I am on page 25 of the Moreplay Upgrade manual. I am confused by the instruction "Check the power supply voltage by measuring DC voltage between the chassis plate and terminal 21." One of my test meter leads goes to terminal 21. Where do I clip the other?
This is to be sure the filters are not charged.
If you can discharge the filters safely you will save 15 min or so.
Andre.

“Without music life would be a mistake”


Offline Colman

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OK, I get it. If I wait 10 minutes, is that enough time for "the high voltage power supply will need several minutes to drain before you can move the clip leads"



Offline AG

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Don't assume regarding time is to risky.
better measure it and be sure is less than 20V.

Andre.

“Without music life would be a mistake”


Offline Colman

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I will measure then. Thanks for your help!



Offline Colman

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Uh oh! I checked the B socket and it measured an acceptable 6.25 V. After 10 minutes, I went to check the chassis. I unplugged the red probe from B2. I forgot I still had the black probe clipped on B7. As soon as I touched the red probe to terminal 21, there was a big spark at terminal 21! I'm unharmed but it really woke me up! Do you think I damaged the Moreplay?



Offline AG

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Bummer!
If the MP was still under power or not the filter discharge.
I will let this answer to @paul, the BH expert.
Did you check again the filament power on both? (6.2V)
Andre.

“Without music life would be a mistake”


Offline Colman

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I rechecked all the voltage values (pg. 59 MP Manual) with the chassis upside down. I got a couple of bad values. Terminal 4 read 0 instead of 7-9, and terminal 6 read 252 instead of 110-140. All other measurements were good. I powered off the MP. After 15 minutes, I turned the chassis right side up and powered up. Turns out the bad measurements are a separate issue: the tube in socket A doesn't light up and there is no sound from the right channel. The left channel is fine. I swapped tubes and remeasured. This time, terminal 4 is 6.54 and terminal 6 is 111. There is no sound from the left channel and the right channel is fine. So the tube is blown.
Both 6V6 tubes were working fine before. I'll just get a replacement pair. It will take some time before they get delivered.
Also, after performing the voltage test I'm sure that my MP survived the spark undamaged.
Questions:
1) How do I test filament power?
2) Can anyone recommend particular 6V6 tubes or their equivalent?