Help with Marshall transformer

[ryanf]

Hey everybody,

I'm starting a Soldano SLO50 (schematic seen here, click on SLO Docs: http://homepage.mac.com/WebObjects/File ... US&lang=en , and I have the Marshall power transformer seen here: http://www.tubesandmore.com/scripts/fox ... m=P-TM-P50


The schematic shows a transformer with 4 wires, but mine only has three. The schematic implies that the bias control needs to come from one of the high voltage lines (red?). So my questions are:

Do I connect the bias control to one of the red wires with a 220k resistor?

If so, do I ground the center tap? I looked at JCM Schematics and it is left unconnected.

I know high gain amps arent very common on this forum but you guys are great, and I would really appreciate any help.

Thanks in advance!

-Ryan

[rhinson]

Hey everybody,

I'm starting a Soldano SLO50 (schematic seen here:http://homepage.mac.com/WebObjects/File ... ing15.html , and I have the Marshall power transformer seen here: http://www.tubesandmore.com/scripts/fox ... m=P-TM-P50


The schematic shows a transformer with 4 wires, but mine only has three. The schematic implies that the bias control needs to come from one of the high voltage lines (red?). So my questions are:

Do I connect the bias control to one of the red wires with a 220k resistor?

If so, do I ground the center tap? I looked at JCM Schematics and it is left unconnected.

I know high gain amps arent very common on this forum but you guys are great, and I would really appreciate any help.

Thanks in advance!

-Ryan

to use that power trannie on a build: yes ground the hv sec. centertap; and yes you roll your own bias supply by coming off either of the hv sec taps with a 220k dropping resistor --from there just build the normal marshall style bias supply you see almost all marshalls and lots of other amps. since this trannie is a jcm800 style power trannie check the schematic at schematic heaven for the bias supply values. rh

http://www.schematicheaven.com/marshall ... w_1987.pdf

[LOUDthud]

The first link in your post seems to be broken, I get the following error:" This published page no longer exists. FileSharing15.html ". From the page on the transformer I think you are correct that the bias supply taps off of one of the red wires with a 220K resistor. Naturally, you need a diode and a couple of caps and resistors to complete the circuit. If you can't get quite enough voltage, you may have to reduce the 220K to 150K or lower. A 2 or 3 watt flame proof resistor is usually used.

[Johnhenry]

I got no problem opening his link
Johnhenry

[ryanf]

I think the link is fixed, but I get the idea. Thanks alot guys.

[Lonely Raven]

Edit: Nevermind, the link started working again.

[rjgtr]

Also go here for some great info on SLO clonemaking -
http://sloclone.yesterdaysrevolt.com/. You'll have register, but it is a good forum with lots of great info.

[ryanf]

Also go here for some great info on SLO clonemaking -
http://sloclone.yesterdaysrevolt.com/. You'll have register, but it is a good forum with lots of great info.

Yea I'm a member there. Its just that they aren't exactly quick to reply.