Hi!
Just aquired a broken marshall jcm 800 4210. I ordered a ptp 2204 board from a guy named Walt from Ebay.
I have installed the board using this layout: http://imagizer.imageshack.us/a/img923/7464/csvXym.jpg
This is the layout for my ptp: http://imageshack.com/a/img924/2359/LcsqP6.jpg
Now... I discovered that my PT did not have an Center tap and that i have to go for a full bridge rectifier and change the bias circuit a bit.
Here is a picture of the actuall board: http://imageshack.com/a/img922/4094/8XNscd.jpg
Can somebody please give me a step by step on what to do?
Best regards
Kennet
Help with diode bridge and bias supply wiring
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Help with diode bridge and bias supply wiring
Kennet Iversen
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Re: Help with diode bridge and bias supply wiring
This is what I have done so far: http://imageshack.com/a/img924/3291/9GgeW8.jpg
Kennet Iversen
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Re: Help with diode bridge and bias supply wiring
So this is what I had to do for the standby switch wiring.marshallnoise wrote: ↑Mon Sep 18, 2017 7:14 pmSeems like something at the bottom of the page would make sense. Am I correct in thinking that half of the rectifier will be seeing AC all the time and the other half will get it when the standby switch is flipped?
http://www.valvewizard.co.uk/standby.html
If you have no centertap on your HT, then you have to do a capacitor coupled bias supply.
And here is the way it is wired up for me.Littlewyan wrote: ↑Thu Sep 14, 2017 7:33 amBecause you have no centre tap on the HT you will need to use a Capacitor Coupled Bias Supply.
http://valvewizard.co.uk/bias.html
Merlin explains it here. It's an odd circuit and you will have to wire up the standby switch a bit differently for it to work properly when the amp is in standby. Also for safety reasons you may want to use a special capacitor. One that is rated for high AC Voltage and I think it shorts when it fails or something? I bought a few. Marshall have used this circuit a few times and I used it in my last build. I can give further details in a few days time if you need them .
IMG_20171024_082925017 by Paul Abbott, on Flickr