hi there, first time posting.
i have a yamaha cr 2020 that was working fine, and just stopping clicking the relay and no sound.
its been recapped, and the service buillitens done. it has 2sd525 replacements.
on TR 714 i have 99 ohms and 0.068 in diode mode, reading between base and emitter. is this normal?
i was thinking this was my problem, but i dont know enough to be sure.
i have plus and -59 volts, but i dont know what else to look for voltage rail wise. any help would be much appriceated.
i have a yamaha cr 2020 that was working fine, and just stopping clicking the relay and no sound.
its been recapped, and the service buillitens done. it has 2sd525 replacements.
on TR 714 i have 99 ohms and 0.068 in diode mode, reading between base and emitter. is this normal?
i was thinking this was my problem, but i dont know enough to be sure.
i have plus and -59 volts, but i dont know what else to look for voltage rail wise. any help would be much appriceated.
Bit thin on diagnostics....
TR714 appears to be part of the regulated power supply (-25V) would be a little surprised if this was the cause for "protection"
The relay is part of the protection circuit, it will not engage if excessive voltage is detected at the amps output or if there is a failure in the protection circuit.
Suggest test for excessive voltage, this can be done by measuring dc voltage at the power amp output wires Left then right channels, the Brown(L) and Yellow(R) wires are marked "O", alternatively you can measure at the input to the protection board, pins are marked "Li" and "Ri". Black probe connected to chassis/GND, ideally 0mV, less than 75mV can be tolerated.
TR714 does not sound heathy, did you do the test in-circuit or did you remove the transistor.
Suggest a basic health check of the power supply, measuire dc voltages at the +/-25 pins/wires.
TR714 appears to be part of the regulated power supply (-25V) would be a little surprised if this was the cause for "protection"
The relay is part of the protection circuit, it will not engage if excessive voltage is detected at the amps output or if there is a failure in the protection circuit.
Suggest test for excessive voltage, this can be done by measuring dc voltage at the power amp output wires Left then right channels, the Brown(L) and Yellow(R) wires are marked "O", alternatively you can measure at the input to the protection board, pins are marked "Li" and "Ri". Black probe connected to chassis/GND, ideally 0mV, less than 75mV can be tolerated.
TR714 does not sound heathy, did you do the test in-circuit or did you remove the transistor.
Suggest a basic health check of the power supply, measuire dc voltages at the +/-25 pins/wires.
Thank you...!! Tr714 tested good out of circuit. Like I said there is 100 ohms between base and emitter in circuit.
I'll look into what you have said.....I just need a little guidance...
I'll look into what you have said.....I just need a little guidance...
ok, well now i have no voltage on those brown and yellow wires. this is getting worse. i do believe i had plus and minus 59vdc at some point, but it seems to be gone now. anyhelp would be apprecated!
not sure if this matters, but when i turn it on it lights up, no relay , takes 3 or 4 seconds and then my amp meter shows .350milliamp draw. that seems ok to me, is it?seems like its turning and drawing current
not sure if this matters, but when i turn it on it lights up, no relay , takes 3 or 4 seconds and then my amp meter shows .350milliamp draw. that seems ok to me, is it?seems like its turning and drawing current
Need to be a bit more thorough, if you don't understand what was requested or how to do something then ask.
Did you check the voltages at the Ri, Li pins on the power supply board. The pins are near the relay.
Ideally you should expect a very low voltage, select the mV scale. Also what did the +25 and -25 pins also on this board show.
Did you check the voltages at the Ri, Li pins on the power supply board. The pins are near the relay.
Ideally you should expect a very low voltage, select the mV scale. Also what did the +25 and -25 pins also on this board show.
That's what I was saying. I have zero voltages at those pins. I'm pretty sure I did have voltage there at one point.
As I've been trying to manipulate these boards around to test, the wires have been breaking off and all that.
I just find the manipulation of these boards to test anything and all the different pins and wires confusing. I need to restore those voltages first.
Any idea where i should look? The BR right after the 17.5VAC doesn't show any DC voltage coming off it but it test OK?
As I've been trying to manipulate these boards around to test, the wires have been breaking off and all that.
I just find the manipulation of these boards to test anything and all the different pins and wires confusing. I need to restore those voltages first.
Any idea where i should look? The BR right after the 17.5VAC doesn't show any DC voltage coming off it but it test OK?
Yeah, access is a PITA, youve probably "blown" a fusible on the electrolytic board.
PSU health check by the numbers,
- 25 Regulated supp;y.
Check TR707 then TR708 Vb then Ve (to GND)
On the 0mV at Ri, Li, sheck power amp fuses F601,2 are ok.
PSU health check by the numbers,
- Check AC between red wires/pins marked AC on electrolytic board.
- Check DC after rectifiers etc at +/-NB pins on electrolytic or power supply board.
- 25 Regulated supp;y.
Check TR707 then TR708 Vb then Ve (to GND)
On the 0mV at Ri, Li, sheck power amp fuses F601,2 are ok.
Exactly where did you test this, at the BR? or R801,2, +/-NB. Probably blown FR801,2.
OK great. I will check on all of this and report back tomorrow. I checked the 17.5vac on the 2 blue wires coming off the transformer Into the powersupply board. (The 2 pins uo on the left of the powersuooly board near the fuse)
I've checked the fusible resistors on the electrolytic capacitors board and they all seem and read fine, expect for 1. Reading in the megoohms ill have to get back to you tomorrow with the ecact one.
I'll be working on it all day tomorrow and be able to post results all throughout the day.
I've checked the fusible resistors on the electrolytic capacitors board and they all seem and read fine, expect for 1. Reading in the megoohms ill have to get back to you tomorrow with the ecact one.
I'll be working on it all day tomorrow and be able to post results all throughout the day.
Yeah, the whole ps should be checked out but that's a big job, I've focused on the 25V supply because you reported a potential problem with TR714.
for 25V supply need to check
Yep, that one has failed, followup and replace.
the red AC wires have 86vac on them. i have 17vac on the 2 blue wires coming into the top power supply board, one is marked BE the other is blank. but they are above and below the 1amp fuse.
im going to pull the electroylitic board out again and check that resistor i was saying was high, because i believe i tested it with a leg pulled and it was ok.
im going to pull the electroylitic board out again and check that resistor i was saying was high, because i believe i tested it with a leg pulled and it was ok.
maybe to help you could explain something, the 2 blue wires above and below the fuse , thats the vac coming from the power tranny, to power up powersupply board 1? and the 2 red wires? same? are those the only VAC inputs coming from the transformer?
im having trouble understanding this schematic mostly
im having trouble understanding this schematic mostly
ok, so the CT i take it is center tap, and from that to each of the red wires, AC/AC i have ;43 VAC on each. that should be correct. AFAIK
am i understanding this schematic correcltly. the role of the electroylic cap board is to generate the 60vdc rails? i have 120vdc on the BR of the electroylitic cap board, i have 60 vdc accros the 2 red resistors. so im pretty sure this board is working correclty? i also have the 60vdc on the pins that connect to powersupply board 1. the molex connector , ive reflowed those, and the entire board.
ok, you can disgregard all pasts posts. i have the 60vdc on both amplifier boards, i have the 43vac inputs. what i dont have is the +/- 25vdc. i do not have that. so i guess, im back to my original problem. 712/713/714/715 all test fine. i do have low ohms on a 715 between emitter and base, 100 ohms. not sure whats up with that.
where can i look to restore the 25volt circuit? or where can i reliablly check for it. ? ive been on this amp all day its driving me nuts.
where can i look to restore the 25volt circuit? or where can i reliablly check for it. ? ive been on this amp all day its driving me nuts.
Not clear if you confirmed Vdc at +/-NB pins. Plz check.
Assuming ok, means TR714, 715 on -ve rail and TR712, 713 on +ve rail.
Measure b/c/e voltages to GND for these 4 transistors (TR712,3,4,5)
With the low Vbe on TR714 (previously measured) replace.
there is no +/- 25vdc on the pins nothing there.
so i cant continue with the rest of your instructions after
assuming ok,?
so i cant continue with the rest of your instructions after
assuming ok,?
+/-NB should be in the range 30-40V.
Are you saying they are 0V or are you saying they are not 25V. One is helpful, the other not.
If +/-NB are 0V then go back to the electrolytic board, the "flow" is,
-AC between red wires
- D801 bridge
-R801,2
-FR801,2
-C805,6
- +/-NB pins (on electrolytic board)
yes nothing on +/- NB. no volts nothing, there is AC betwee red wires, 44 volts between each red wire and CT
ill cheeck the other stuff you mentioned and report back tomorrow. appreciate your help.
ill cheeck the other stuff you mentioned and report back tomorrow. appreciate your help.