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Supro Thunderbolt info

4/22/2006 9:42 PM
Greg SimonSupro Thunderbolt info
I posted to AX84 with some updated voltage info from looking at 3 vintage Supro Thunderbolts, and I'm posting the voltage info here in case anyone wants it. I've also emailed it to Sean Weatherford, so hopefully he'll be able to update his schematic and post a link at AX84. All of the info I'm posting will be in reference to his schematic.  
Right after bridge rectifier = 410v  
Node D = 402v to 407v  
Node C = 395v to 400v  
Node B = 350v, or 390v depending on vintage of amp  
Node A = 275v, or 320v, again depending on vintage of amp  
The early amps with a tube rectifier had a 27k dropping resistor as shown on Sean's schematic. Later, they changed to a solid state rectifier, and some amps still had this 27k. Later, they changed that to a 1k. The later amps had an added row of terminal strip along the back of the amp for the diodes in the power supply.  
There are a couple other things. The can cap is a 20uf/10uf/10uf @450v. The filter cap inside the chassis is a 20uf @ 450v, but, it is wired in parallel with the 2nd node, the 10uf in between the 27k and 1k resistors, so the total at that point is 30uf. There is a .1uf 600v cap to ground towards the preamp area that is acting as a filter cap for the first stage in the amp.  
The cathode resistor on the preamp cathode is a 3k9 on all of these amps instead of the 3k3 that is shown. The 110k that is shown to ground in the tone control area is a 100k instead. Also, in the phase inverter section, the parts hooked to each cathode should be switched between tridoes. So the 3k9 should go to the triode on the right, and the 2k2 and 35uf cap should go to the triode on the left. Also, the 240k on top of the first triode should be a 270k. Other than those things, Sean's schematic looks correct, and is certainly way easier to read than the other one available.  
Hope this is of use to people, and check at AX84 or Sean's site for an updated schematic in the next couple weeks hopefully.  
Greg Simon

bob p Greg, at what value did you clamp t... -- 4/23/2006 12:10 AM