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pyramid 22 amp power supply

M

Mcds26

Member
Apr 1, 2006
27
0
11
Cali
I was using it with a small amp and then it went dead .... turned it off then let it sit turned it back on andwent to 12 volt were i had it set then fell to nothing so i replaced the 2n3055 transistor and stell doing the same thing ...... turns on gos to 12 volt then to 0 volts any help on this one ? thanks for your time
 

Mcds26 said:
I was using it with a small amp and then it went dead .... turned it off then let it sit turned it back on andwent to 12 volt were i had it set then fell to nothing so i replaced the 2n3055 transistor and stell doing the same thing ...... turns on gos to 12 volt then to 0 volts any help on this one ? thanks for your time
Click to expand...
.......you mentioned replacing "the 2n3055"...did you check the others? They mostly have 4 pass transistors in that amperage range. If yours has the "crowbar" overload protection circuit.....good idea to replace the SCR. Most of the time when the pass transistors short out, the voltage regulator IC goes with it. (KX and the Gold series) I hope this helps.....73's
 
I just finished looking at a schematic of a 21 and didn't see a SCR but dosen't mean it not there. Look for a transistor on a heat sink that looks like a CB final, starting with a TYN prefix (TYN-682, 692) worth a shot. May have a different number so the NTE-ECG cross reference comes in handy. If you start with voltage that drops quick, somethings getting hot fast. I would have changed all of the 3055s and for good measure the 723 voltage reg IC. Also you might want to set voltage at 13.8 to 14.
 
yeah i found that tyn 690 c219a when i pull it i will get the full number .. I thank you guys for all the help and i did replace all 4 of the 2n3055 now i just need to fined a place to get the tyn 690
 
cool.....but to be on the safe side, I'd replace the voltage regulator as well. Like I said when the 3055s go they take the reg with it. Look for an IC chip that has xx723, I buy a socket and solder it in first (after the old chip is removed of coarse) then you don't have to worry about too much heat on the new one from the soldering.
 
I've seen alot of the Pyramids go out with regards to the 2N2035's, but I've never seen one blow a chip or an SCR yet. In the case of this supply, is the voltage there when you turn it on, but drops when you try to run anything on it? If so, it just sounds like pass and/or drive transistors failing
 
PLUTO said:
Mcds26 said:
I was using it with a small amp and then it went dead .... turned it off then let it sit turned it back on andwent to 12 volt were i had it set then fell to nothing so i replaced the 2n3055 transistor and stell doing the same thing ...... turns on gos to 12 volt then to 0 volts any help on this one ? thanks for your time
Click to expand...
.......you mentioned replacing "the 2n3055"...did you check the others? They mostly have 4 pass transistors in that amperage range. If yours has the "crowbar" overload protection circuit.....good idea to replace the SCR. Most of the time when the pass transistors short out, the voltage regulator IC goes with it. (KX and the Gold series) I hope this helps.....73's
Click to expand...
That's what happened to my PS 21 KX.when I accidentally made contact with the pos and neg and the little caps on the voltage regulator swelled and two out the four 2N3055 transistors blew.
 
DTB Radio said:
I've seen alot of the Pyramids go out with regards to the 2N2035's, but I've never seen one blow a chip or an SCR yet. In the case of this supply, is the voltage there when you turn it on, but drops when you try to run anything on it? If so, it just sounds like pass and/or drive transistors failing
Click to expand...


turn it on with nothing hooked up to it and drops then when it is off after that and your turn it back on you get nothing ...


on - 12 volt drops to 0.25
off -
on - 0.25 volts
 
DTB Radio said:
I've seen alot of the Pyramids go out with regards to the 2N2035's, but I've never seen one blow a chip or an SCR yet. In the case of this supply, is the voltage there when you turn it on, but drops when you try to run anything on it? If so, it just sounds like pass and/or drive transistors failing
Click to expand...
.......I repaired a Pyramid 36(35 actual) amp not too long ago, which took the 2N3771 transistors, the SCR (cracked and crispy) and replaced the reg IC. The dude blew a fuse trying to run too big of a amplifier......didn't have an extra, so out comes the aluminim foil.....soon to be followed by his wallet. I just mostly change the voltage reg when the passes go, that way I know it's ok. If I have a SCR handy I'll change that also while I'm in there, if the supply was 10-7 due to being overloaded.
 
Well got all the parts but the scr replace and tryed it and nothing does not even volt up and drop off again so i came i tryed it is stell broke so here it go's to the rack and will sit there intel i fined a scr for it thanks for all the help guys just wanted to try see ya
 

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