swr workingman 15 trouble

[DrGonz78]

what i did is i hooked up the bulb in series to what i believe is the hot , which resembles the schematic as its seen from inside the amp facing. hot on the right nuetral on left. Now to be clearer if i was behind the amp looking at the plug and connecting it the hot would be on the left and nuetral on the right . In a position as if i were plugging it in . Does that give the right picture??

You have it right as far as function is concerned and the hot side is the fused side. However, the power switch shows three connections 1, 2 and 3. 1 and 2 break the hot side of the circuit open to closed to turn on and off. The 3rd connection of the switch, as far as schematic is concerned, connects to the neutral side. Was the bulb lit up bright as could when you had the unit on?

"Note: for switch to light up while bulb was lit at same time i jumpered from conn.3 on switch to the hot side of mains in before fuse."
So going by what you just explained here it would look like this...

[zairec14]

that is correct and as far as the bulb it was lit up like if it was in a fixture as usual i suppose. give me a few and ill line up the limiter i built exactly to your instructions and well start from there once more and ill report

[zairec14]

sorry for the delay. OK limiter set successful. switched it on and the bulb was brighter than when i first tested the limiter before i powered on . But i mean substantially brighter! back to drawing board?

[DrGonz78]

I hope you are using an incandescent light bulb, are you? If yes then do some more quick voltage tests of the power rails and lets see if the voltages are now lower with the light bulb limiter in place. Just a quick test to compare what they were to what they are now. Just for the learning experience of it. Even just test the -/+15v rails to see if they are lower.

[zairec14]

I couldnt sleep Im up and what i have less than 1 DC at the top of the r1/r2 resistors although i do have -/+ thats a plus ! give or take on the pun... lol *@$%# ive checked the transistors throughout none are suspect . ill check again. im gonna stare at the schematics till i get sleepy. maybe i can use compulsiveness as a tool to zero in on anything.

[zairec14]

yes incandescent

[zairec14]

i noticed something on the schematic (pre amp psu) page 2 c-6.
coming from the BR w2. That is off board . connects to board via BR1. Does D7 seem like it gets unrectified voltage direct from the AC side of the off board bridge? If it does I dont have that making a connection that way . Am i understanding that correctly?

[zairec14]

ion the schematic i preamp and psu page 2 c-6 i saw that d7 has a direct connection from offboard bridge AC to board . If i can get some opinions on this ive isolated the pad on board directly connecting to d7 diode . Question is can that be the proper connection for the secondary,s middle wire (yellow)? Or is it as schematic leads me to think it suggests that its from the actual point that itleaves the offboard bridge ?

[DrGonz78]

So we have almost no voltage on the power rails and I forget if this is the first time we measured those rails since putting the center tap back into position. With the amp off I would test the Bridge rectifier in circuit to check with meter using diode setting. As far as that D7 connection and other things we need to take all this very slow and careful. Can you post some clean picture of the various points in the amp?

[Enzo]

On top of the main bridge is "AC". That is what connects to D7. D7 is an independent small supply that charges C7 to turn off the power amp mute, Q1,2.

The red/yellow center tap wire from the transformer connects to POWER GROUND. Look left of the speaker jacks to W15, and upper left W10,11.

[zairec14]

theres a power ground to the right of the output fuse and theres a ground to the right of the big filter cap. it might say pgrnd but its partly obstructed by the cap. that pgrnd by the fuse near the jacks has a wire grounding the jacks already. i might of mis placed that there if i misread the schematic

[zairec14]

hi whats the power amp mute ?

[zairec14]

upon further inspection and a double check of all transisitors a i came to find Q2 base was broken . Q2 is directly inline with D7.
that doesnt shed light on the low voltage. . That may have been the cause of the (NO SOUND AMP ON EFFECT) possibly?. oooops scrratch that it blew the emitter leaving a searing hole on the bottom. cant believe i didnt see that before. that has to be more recent.

[DrGonz78]

hi whats the power amp mute ?

At turn on this circuit mutes the output of the amp for a few seconds or so. Makes turn on pops go away and I think it might help mute amp at turn off too.

upon further inspection and a double check of all transisitors a i came to find Q2 base was broken . Q2 is directly inline with D7.
that doesnt shed light on the low voltage. . That may have been the cause of the (NO SOUND AMP ON EFFECT) possibly?. oooops scrratch that it blew the emitter leaving a searing hole on the bottom. cant believe i didnt see that before. that has to be more recent.

Fact is that the light bulb we had originally trying to limit current was not really working the way it was installed. All the rail voltages I have seen measured so far were not limited by the bulb and there was unlimited current draw available to the amp. When you say the Q2 base was broken does that mean the leg was cracked? Possibly HV+ is now shorted across that Q2 connection?