question from noob that seaches about G7 PSU

[marktokach]

I have tried all search functions and scrapbook plus which is helpful, but still have problems finding things. I need a little help with wiring the mains and iec fused connector on the the G7 psu. The switch i have is a carling SPST fender amp switch. it has only 2 connections. i have an iec connector with fuse. Will this work? I have it hooked up and its blowing fuses.I think i have it hooked up wrong. I have read it's better to have a Dual ON-OFF Double Pole, Single Throw = DPST. Does it really matter? It seems easier to hook up with DPST because it has at least 4 connections. I read it's safer too because it disconnects both neutral and hot at once. I have to order this one and want to get this working already. Can I safely use spst and does it go on the hot side or neutral or doesn't it matter? TIA

 

[pucho812]

take it in baby steps. For starters, blowing fuses notes another possible issue or you have a wrong  value fuse. Ideally your looking and hot, neutral and ground.  lets assume your ground is connected properly.  the neutral is going to go directly to the Power transformer. The hot will go to the fuse, then out of the fuse into the switch the other end of the switch will go to the transformer. A SPST switch is o.k. to use I have done that before without issue. 

 

[marktokach]

Thanks that helps and I do have it hooked up wrong. You guys are great at helping!

 

[pucho812]

your welcome.... at least it was just a fuse that went pop vs something more expensive

 

[marktokach]

I got the new slow blow fuses and they aren't blowing. I am trying to test the pins from the 7 pin xlr jack with my fluke 87 III with no mic hooked up on voltage setting. I am not sure how to test. I  put the black in the pin that has ground wire, and red in all others. I got 11.27 v, 2 mv, .675 v, .682 v, 2 mv , .567 v. I'm obviously not sure how to check the voltages or I have a problem. Is there a link someone can point me to I am not finding? This is my first project without instructions.

 

[Blue Jinn]

I'm not an expert by any means. I just built a Royer circuit with BigUgly's PSU.  I get different voltages with the mic plugged in vs unloaded. I just built another one, and slapped a 300k resistor on as a dummy load and the values stayed the same (different trafo and a smaller R1 -- what I had on hand...)

The voltages (except for the .567) seem like they are off by a factor of 10? Also, why not test from the PCB outputs rather than the XLR, I don't know why it would make a difference, but at least you eliminate a variable that way. I would test the AC going in just to make sure those values make sense too. I had kind of  a hokey setup on my first PSU, and I only get 71 volts from a 120-12v wired backwards with 9v on the secondary. That gave me 99v unloaded on the output, which drops to 71v loaded. It's kinda low, but the mic works so I'm not complaining. (It's the stock single sided 32mm K67 clone capsule) I'm going to try it with the proper volgtages as soon as I finish the second PSU.

I do have 120 to 135/9v transformers I had custom wound for this if you need another transformer.

 

[marktokach]

Do I just touch neg probe to any ground and then the other points? Do I touch it to chassis? I get different readings either way.

 

[Blue Jinn]

Take a look at the file gic_psu.pdf. At the PSU B+ and Heater have separate grounds. Looking at the PSU board, with the big caps to the left from top to bottom you have (1) Heater 0, (2) Heater +, (3) Ground, (4) B+, (5) Pattern.

So you should measure (neg)Black (1) (pos) Red (2), and this should be around 6.3VDC. Then Black (3) Red (4) this should be around 160VDC give or take.  then you should measure Black (3) red (5) and this should vary between 0-160 depending on the switch setting.

Note that you are measuring this without a load, but will let you know if your PSU is in the ballpark.

 

[marktokach]

Here are some results of voltage test. They don't look good. I got a couple of sparks 2 times when i slipped with the probes. Ever feel like chucking everything out the window?

 

[zayance]

Looks like a Short somewhere, Homemade PCB?
All components in the right place and right direction? EDIT: Rectifier Packages in the right direction?
I guess the Power transformers will heat up because of that,
so be carefull....

 

[Blue Jinn]

You mentioned you get readings with teh negative on teh chassis. Check for shorts as teh PCB doesn't have a chassis ground. Try disconnecting the XLR's  if that is possible and removing the PCB from your chassis and recheck the voltages.

 

[marktokach]

It is a rev 2 pcb that someone made. I have it out of the chassis, no difference. I'll post some pics soon. Thanks!

 

[zebra50]

Are those AC or DC voltages?

 

[marktokach]

I have it set to ac, so ac.

 

[gyraf]

psu is an ac-to-dc conversion thingy, so you need to measure dc at it's output(s)

 

[marktokach]

Like Duhhhhhh! I guess I should have known that. I read it a thousand times! Funny how you can miss the obvious sometimes. That was it. It works! Now just gotta figure out the 6 wire mogami 7 pin amphenol connector issue.