J4-1

a DIY, modified Mullard 5-20 monoblock design

J4-1

Postby Marshman » Sun Sep 25, 2005 3:01 pm

I must just be dense. I have wired the switch in as follows:

Pin 1 = from fuse/black 120v
Pin 2 = one side of the PT primary
Pin 3 = to J4-1

J4-1 = From Pin 3 AND other half of PT primary
J4-2 = white from 120v

I am only seeing 37ish volts at J4-1 and J4-2 instead of 65ish.

All other voltages and resistances seem correct.

any suggestions?

Thanks!
mm
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Re: J4-1

Postby Shannon Parks » Tue Sep 27, 2005 6:29 am

Marshman wrote:I must just be dense. I have wired the switch in as follows:

Pin 1 = from fuse/black 120v
Pin 2 = one side of the PT primary
Pin 3 = to J4-1

J4-1 = From Pin 3 AND other half of PT primary
J4-2 = white from 120v

I am only seeing 37ish volts at J4-1 and J4-2 instead of 65ish.

All other voltages and resistances seem correct.

any suggestions?

Thanks!
mm


Hi mm,

Your wiring looks correct. From where are you referencing the AC - the safety ground or the PCB (or have you tied a jumper to the chassis already)?

Actually, I question if this isn't really a good measurement to make after all. Maybe we should just measure from J4-2 to pin 1 of the ON/OFF switch to verify 120VAC.

Shannon
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Postby Marshman » Tue Sep 27, 2005 8:20 am

I checked it both from J4-1 (and J4-2) to chassis and to PCB ground. I do not have a jumper to the chassis from the PCB (yet).

It just seemed odd to have half voltage there, but the secondary is fine? Could it have something to do with R46?

mm
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Postby Marshman » Tue Sep 27, 2005 5:35 pm

I tried firing it up tonight. It took about 15 seconds to warm up, then started making a loud putt-putt-putt noise in the speaker.

I had the meter on the bais TP1 and it appeared to be about 300mv or so... no smoke, nothing seemed to be getting hot, but the filiments did not seem very bright if even fired up at all.

Any suggestions?

mm
Marshman
 
Posts: 34
Joined: Mon Jul 18, 2005 12:43 pm

Postby Shannon Parks » Wed Sep 28, 2005 7:45 pm

Marshman wrote:I tried firing it up tonight. It took about 15 seconds to warm up, then started making a loud putt-putt-putt noise in the speaker.

I had the meter on the bais TP1 and it appeared to be about 300mv or so... no smoke, nothing seemed to be getting hot, but the filiments did not seem very bright if even fired up at all.

Any suggestions?

mm


Thanks for the photos, mm. It does appear your phases are swapped on J2 & J3. Easy fix!

Shannon
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Postby Marshman » Thu Sep 29, 2005 5:22 am

Thanks Shannon!!!

I knew it would be something simple and stupid on my part. I really quick fired it up before work this am and it sounds fine!!

Thanks again!!

mm
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