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    The bulb will react differently on a solid state...

    The bulb will react differently on a solid state vs. a tube amp. Solid state should be bright, get dim, and stay that way. Tube amps will depend if you have a standby switch or not. I would agree...
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    Transistors can test OK with a DMM or tester and...

    Transistors can test OK with a DMM or tester and fail in circuit, as the testers use very small voltages (maybe 5v). The saying I've seen is that a tester can tell you if a part is bad, but not that...
  3. The KLD boards have components....

    The KLD boards have components. https://www.ebay.com/itm/Turret-board-soldered-components-Fender-tweed-Bassman-5F6A-DIY-guitar-amp-kits/273789603273?hash=item3fbf21cdc9:g:XCwAAOSwqVdapyqp You would...
  4. Looks like the OT on this amp is an ultralinear...

    Looks like the OT on this amp is an ultralinear type, correct? I wonder how well these do for lower powered amps.

    There is a company called KLD that sells PCBs and turret board kits for tube amps...
  5. Have you replaced the shorted transistors? I...

    Have you replaced the shorted transistors? I think in general the smart thing is to replace transistors at least one stage upstream from the ones that failed, so if the O/P transistors fail replace...
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    So when you do this is it with a dim bulb? Are...

    So when you do this is it with a dim bulb? Are the 40V and 90V rails symmetrical?

    On your "bright bulb" voltages it looks like something is really pulling down the negative voltages. Can you...
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    I think the more interesting data would be the...

    I think the more interesting data would be the voltages driving the power transistors.

    I don't know that resistance readings of transistors while in the circuit are going to be helpful (other...
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    I think you are probably at a point where you...

    I think you are probably at a point where you need to start taking some voltage readings and using those to guide the search. You can do it for both sides of the amp and use the ones that seem right...
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    I can't see any reason for the BC807 part to...

    I can't see any reason for the BC807 part to cause an issue (especially at idle), assuming the pinout of the two parts is the same.
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    R2K is a terrible way to mark a transistor.

    R2K is a terrible way to mark a transistor.
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    I'm confused, is this for Q112? Is yours actually...

    I'm confused, is this for Q112? Is yours actually a resistor not a transistor? Was the original actually bad then?
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    Looking at the schematic it looks to me like Q112...

    Looking at the schematic it looks to me like Q112 and Q109 are implementing some negative feedback from the last output stage back to the driver stage. The voltages and currents seen by these...
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    I use the free version of easyeda.com to do my...

    I use the free version of easyeda.com to do my layout and then ordered from them. You don't have to buy from them as you can download gerber files, but it was really easy to order from them and the...
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    You may not get too much warmth at the IC since...

    You may not get too much warmth at the IC since the voltage there is so low, and those resistors are actually dissipating most of the power.
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    You have a problem with the output of the...

    You have a problem with the output of the amplifier and it is sending DC voltage to the speaker. It will burn up the speaker pretty quickly if given a chance.
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    So you have something on the +/-15V rails that...

    So you have something on the +/-15V rails that are pulling them way down. Looks like the the +/-15 that goes to the XR header is off from proper voltage regulators V100 and V101 so the AMP IC supply...
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    They are designed to drop the 10V difference...

    They are designed to drop the 10V difference between the +/-25V and the +/- 15V set by the zener diodes. 10V across 220 ohms should only be about 1/2 a watt (using V^2/R), which to me shouldn't be...
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    Since we are still beating this horse, it seems...

    Since we are still beating this horse, it seems odd that the schematic calls out "7204" not "SDS-7204". They don't drop letters for other parts, or if they do they list it both ways in the cross...
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    This to me just doesn't look like it will fit at...

    This to me just doesn't look like it will fit at TO-202 package. I also don't see the 205v max voltage since the collector of Q106 is on a +25V rail. It is driving the base of a 1 A transistor (Q108)...
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    It's not like this is the only part that got...

    It's not like this is the only part that got fried in the unit.
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    56012 Does it have the AC line connected to...

    56012

    Does it have the AC line connected to the chassis or is there an IEC connector (like on a desktop computer)? You should have a black, white, and a green wire coming off the AC cord if there...
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    Amplifiedparts has the original in stock and...

    Amplifiedparts has the original in stock and looks like they ship internationally. https://www.amplifiedparts.com/products/transistor-peavey-sds-7204-300v-10ma
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    To educate me, I don't understand how a 300V 10mA...

    To educate me, I don't understand how a 300V 10mA rated transistor can be a 10W device, that sounds to me like 3W or less, but I can't find any info other that that on these parts. I have never...
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    Just curious why you think this needs a 20W...

    Just curious why you think this needs a 20W transistor?
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    I see 7204 spec'd as a 300V 10mA NPN transistor,...

    I see 7204 spec'd as a 300V 10mA NPN transistor, but I have no idea why you would need such a high voltage rating for Q106, since it is on a 25V rail. There should be many TO-92 NPNs will work there....
  27. There are cheap x100 probes sold on ebay that...

    There are cheap x100 probes sold on ebay that claim high voltage rating, but I wonder if they really can handle it? I guess you could test it by "probing" a high voltage source without the probe...
  28. The probes will also have a max voltage spec,...

    The probes will also have a max voltage spec, which is basically how much power the voltage divider resistors inside can take. Often it is no more than the 300V that the scope input is rated for....
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