Hi,
I have a citation 16 and someone was helping me diagnose this issue
They had me remove main PC board for the channel
disconnect the power caps
and i replaced the rectifier with original replacement
the intent was to remove the output transistors from the circuit by removing the board and power caps that the only thing in the circuit is the rectifier and the power supply/transformer
Not sure this is accurate since 2 wires from the recitfier are connected to the circuit in the heat sink
Still blows fuses
Next
pulled all the output transistors and tested with these results
two of the original output transistors were shorted and replaced with MJ15024G
I dont have a variac but will get one so i can see what kind of voltage is at the rectifier
I checked all the emitter resistors in the heat sink and they all test .5 - .6 ohms
i checked all the resistors for shorts and no shorts
checked the two caps (in the heat sink) and both are above 10uf the spec
I also checked the main power caps and all in spec or close to (although they are not in the circuit)
I have a citation 16 and someone was helping me diagnose this issue
They had me remove main PC board for the channel
disconnect the power caps
and i replaced the rectifier with original replacement
the intent was to remove the output transistors from the circuit by removing the board and power caps that the only thing in the circuit is the rectifier and the power supply/transformer
Not sure this is accurate since 2 wires from the recitfier are connected to the circuit in the heat sink
Still blows fuses
Next
pulled all the output transistors and tested with these results
| left heat sink | |||||||
| left row | right row | ||||||
| B-C | B-E | C-E | B-C | B-E | C-E | ||
1 | 0.507 | 0.518 | 0 | 0.505 | 0.519 | 0 | |
2 | 0.495 | 0.518 | 0 | 0.492 | 0.511 | 0 | |
3 | 0.516 | 0.527 | 0 | 0.510 | 0.521 | 0 | |
4 | 0.517 | 0.527 | 0 | 0.517 | 0.529 | 0 | |
5 | 0.517 | 0.528 | 0 | 0.515 | 0.526 | 0 |
two of the original output transistors were shorted and replaced with MJ15024G
I dont have a variac but will get one so i can see what kind of voltage is at the rectifier
I checked all the emitter resistors in the heat sink and they all test .5 - .6 ohms
i checked all the resistors for shorts and no shorts
checked the two caps (in the heat sink) and both are above 10uf the spec
I also checked the main power caps and all in spec or close to (although they are not in the circuit)
Without several detailed photos of what has been done, it will not be easy to help.
You have to start from the base, check the on/off switch then the primaries of the transformers, then the secondaries, then the rectifiers and so on, but for that the driver cards must be disconnected.
It is also necessary to specify if it is a 16 or a 16A
You have to start from the base, check the on/off switch then the primaries of the transformers, then the secondaries, then the rectifiers and so on, but for that the driver cards must be disconnected.
It is also necessary to specify if it is a 16 or a 16A
Hi thanks for the reply
left channel board is removed
when i turn the amp on (switch) the right channel goes on and does not blow the fuse
the only thing that has been replaced is the rectifier and 2 output transistors
This amp was working and then had a little distortion.
I have a second working citation 16 amp that I had recapped
I was doing the same thing to this one when the fuse blowing began
All i did was recap the PC boards as i had in the the other amp
Both amps are 16 not 16A
The only difference between them is my working amp has external fuses
The broken amp has fuses inside the case
i have checked all the emitter resistors and caps in heat sink all in spec
Check supply voltages on the following
Primary
Secondary
Does it have a relay? Is it getting enough supply?
remove your outputs and check all the bias of your pre driver and vas stage and check dc offset
check resistors if there are any rusting, fuse supply filter caps and rectifier
Primary
Secondary
Does it have a relay? Is it getting enough supply?
remove your outputs and check all the bias of your pre driver and vas stage and check dc offset
check resistors if there are any rusting, fuse supply filter caps and rectifier
Last edited:
These are the output transistors in left heat sink
Hi for the on off switch if the switch were bad would the right channel power up properly and left channel fail?
i used a dim bulb tester with 100W bulb
powered on fuse did not blow
good channel rectifier reads 52V
bad channel rectifier reads .44V
front lights did not turn on i guess voltage too low?
Hi
With a dim bulb tester with 300W bulb
the good side of the amp show 24V across the rectifier
The bad side show .8V
suggestions? Is it a bad transformer?
With a dim bulb tester with 300W bulb
the good side of the amp show 24V across the rectifier
The bad side show .8V
suggestions? Is it a bad transformer?
Carefully measure the AC voltage at the primary windings,
ie, between BLACK(pin 1) and BLACK/WHITE(pin 3) wires
repeat for BROWN(pin 4) and BROWN/WHITE(pin 6) wires
repeat both measurements on other side.
Why are these caps not connected? To confirm short on this channel?
You've replaced some caps? recheck orientation.
ie, between BLACK(pin 1) and BLACK/WHITE(pin 3) wires
repeat for BROWN(pin 4) and BROWN/WHITE(pin 6) wires
repeat both measurements on other side.
Why are these caps not connected? To confirm short on this channel?
You've replaced some caps? recheck orientation.
Hi thank you for the help.
Bad Channel
With 300W dim bulb tester I measured
BLACK(pin 1) and BLACK/WHITE(pin 3) wires = 12.62V AC
BROWN(pin 4) and BROWN/WHITE(pin 6) wires = 12.63V AC
This is with the CAPS reconnected
Ans PC board connected
Good Channel
BLACK(pin 1) and BLACK/WHITE(pin 3) wires = 12.48V AC
BROWN(pin 4) and BROWN/WHITE(pin 6) wires = 12.30V AC
I'm guessing transformer ok?
readings at rectifier with 300W dim bulb tester
Bad Channel
.85V DC
Good Channel
32.7V DC
Bad Channel
With 300W dim bulb tester I measured
BLACK(pin 1) and BLACK/WHITE(pin 3) wires = 12.62V AC
BROWN(pin 4) and BROWN/WHITE(pin 6) wires = 12.63V AC
This is with the CAPS reconnected
Ans PC board connected
Good Channel
BLACK(pin 1) and BLACK/WHITE(pin 3) wires = 12.48V AC
BROWN(pin 4) and BROWN/WHITE(pin 6) wires = 12.30V AC
I'm guessing transformer ok?
readings at rectifier with 300W dim bulb tester
Bad Channel
.85V DC
Good Channel
32.7V DC
Tranformer primary is getting voltage, means the thermal switch on heat sink and voltage selector are ok. 0.85Vdc at rectifier is bad.
Suggest disconnect the "load" from the rectifier and see if the voltages normalise, ie, need to disconnect the blue marked wires, then measure dc voltages at the rectifier at those wire positions.
Suggest disconnect the "load" from the rectifier and see if the voltages normalise, ie, need to disconnect the blue marked wires, then measure dc voltages at the rectifier at those wire positions.
removed the two load wires on bad channel
bad Channel
tested from red wire to red wire = 1.7V DC
from one red wire to empty load connector .48V DC
from other red wire to empty load connector 164mV DC
Good Channel
tested from red wire to red wire = 10.9MV DC
from red wire to load connector 46.1V DC
from other red wire to load connector 46.8V DC
I'm clueless...i have 3 rectifiers and have tried all three same results (2 are original HK rectifiers the third is from Patrick Krausharr (HEXFREDS Rectifier currently installed) who was helping me but I'm afraid he is ill or worse, he has a bad heart condition)
i'm thinking it's not transformer (based on your test) , i tested the main filter capacitors and while old they are close to spec
During this test the PC board was removed also
even with the caps disconnected i get a fuse blow
I checked all the emitter resistors in heatsink and all seem in spec .5 to .7 ohms
i guess i can pull the output transistors AGAIN and test for shorts. I know they are currently a mix of RCA and MJ10524G
i was going to order 2 more MJ10524 and two MJ10522 as the drivers
bad Channel
tested from red wire to red wire = 1.7V DC
from one red wire to empty load connector .48V DC
from other red wire to empty load connector 164mV DC
Good Channel
tested from red wire to red wire = 10.9MV DC
from red wire to load connector 46.1V DC
from other red wire to load connector 46.8V DC
I'm clueless...i have 3 rectifiers and have tried all three same results (2 are original HK rectifiers the third is from Patrick Krausharr (HEXFREDS Rectifier currently installed) who was helping me but I'm afraid he is ill or worse, he has a bad heart condition)
i'm thinking it's not transformer (based on your test) , i tested the main filter capacitors and while old they are close to spec
During this test the PC board was removed also
even with the caps disconnected i get a fuse blow
I checked all the emitter resistors in heatsink and all seem in spec .5 to .7 ohms
i guess i can pull the output transistors AGAIN and test for shorts. I know they are currently a mix of RCA and MJ10524G
i was going to order 2 more MJ10524 and two MJ10522 as the drivers
above measurements are still with dim bulb 300W tester
otherwise the fuse blows immedialty
i am attaching a video i took with the probes on red wire and load wire
the voltage isnt huge?
otherwise the fuse blows immedialty
i am attaching a video i took with the probes on red wire and load wire
the voltage isnt huge?
You need to remove those two red fabric wires from the bridge on the bad channel. Those are probably the transformer secondary wires.
It looks as though the bridge is hooked up wrong. I can't see the diode symbol on the right one. Or it may be damaged. I'd recommend a modern bridge where you hook up the two transformer wires to the wiggle terminals (AC) and the + and - terminals to the appropriate wires from the load capacitor. https://www.newark.com/vishay/vs-kbpc804pbf/bridge-rectifier-single-phase/dp/19M4422
These modern bridges don't have holes for the wires, so you have to bend a loop in the leads with pliers when you don't have a PCB to mount the bridge on. Or you can get an old fashioned one with holes from electronicsurplus.com or surplussales.com . You want 400 piv minimum, 1000 piv maximum, 8 amps minimum, not fast or ultra fast diodes, not schottky diodes.
"capacitor measures almost correct" is a matter of degree. Dried up e-caps usually read about 10-25% high in value. ESR is 2 or 3 times value of a new part, but an ESR meter costs $120 now.
It looks as though the bridge is hooked up wrong. I can't see the diode symbol on the right one. Or it may be damaged. I'd recommend a modern bridge where you hook up the two transformer wires to the wiggle terminals (AC) and the + and - terminals to the appropriate wires from the load capacitor. https://www.newark.com/vishay/vs-kbpc804pbf/bridge-rectifier-single-phase/dp/19M4422
These modern bridges don't have holes for the wires, so you have to bend a loop in the leads with pliers when you don't have a PCB to mount the bridge on. Or you can get an old fashioned one with holes from electronicsurplus.com or surplussales.com . You want 400 piv minimum, 1000 piv maximum, 8 amps minimum, not fast or ultra fast diodes, not schottky diodes.
"capacitor measures almost correct" is a matter of degree. Dried up e-caps usually read about 10-25% high in value. ESR is 2 or 3 times value of a new part, but an ESR meter costs $120 now.
As above, measure AC voltage at the two red wires, near 0Vac points to open secondary transformer winding.
Don't see a case (yet?) for replacing drivers or outputs.
Don't see a case (yet?) for replacing drivers or outputs.
I think you are right i have the rectifier wired wrong. dumb move...basically as i desolderd each wire from original rectifier i soldered the one wire at a time to make sure i did it correct....but if you have the diodes in the wrong orientation .......
I am not home right now but will rewire tonight...i think you found the issue.
Thank you for your help!
the rectifier was wired incorrectly and now the fuse no longer blows!
on to my next issues (probably all created by me) so the bias is 60V (one lead on emitter resistor and the other in speaker output terminal)
on positive terminal 1.5MV on negative terminal 66V! VR2 does not adjust at all and it is a new multi turn pot
At the speaker terminals im getting 60V DC too. and VR1 has no effect to adjust (also a new multi turn pot)
This is with the boards i have modified.
So next step (I have another working citation 16) I will take working board from my other citation 16 and see if i can adjust bias and output properly). if that works then I will starting going through my updated boards and try to find the issue
With good working board from my other citation i was able to get the right channel (the one not blowing fuse) to bias at 10mv and speaker output to 10mv and stayed rock steady after 15 mins.
Then took other board from my working 16 and put in left channel and fuse blew...wanted make sure board was ok so put in right channel fuse did not blow and was able to bias
So. I think either bad output transistor on left channel or the mix of RCA and MJ transistors is causing the issue.
I can buy more 2 more MJ10524 and two MJ10522 to have all the outputs the same...