No overload then... a short is very bad
So 50V you have is fine... if you have too low impedance or short, as Amplifier makes signal, pins 7 and 10 will head toward 0V (maybe you’ll see it dip toward -20V or So)
I recommend not trying to short outputs...these are unobtanium
If amplifier will not come out of protect on power on (safety continuously flashing) check for DC offset
So 50V you have is fine... if you have too low impedance or short, as Amplifier makes signal, pins 7 and 10 will head toward 0V (maybe you’ll see it dip toward -20V or So)
I recommend not trying to short outputs...these are unobtanium
If amplifier will not come out of protect on power on (safety continuously flashing) check for DC offset
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By accident i shorted main speaker output left directly into right! top stupidity
, amplifier was idle, no signal going out at that moment, but amplifier was turned on. after this accident amplifier was still working, until it was switched off, after switching on relay was not working anymore. just tested IC601, exactly 2.8V on pin 12.
R630 is ~560 ohm
it is 28.6v on relay pin from R630
SV1 2004A is warm now.
Q701, q703, q602, q604 are really hot. q603 is so hot cannot keep the finger on.
both yellow and green lights are nicely on, relay is not. it is quite strange.
voltage drop over relay coil is 0,1v
at Q608 collector is 0,1v
tried gently and not very gently tapping and wriggling relay, no action.
Hi, ive just been testing mine also, using the schematics in the service manual ad the advice in this thread.
IC601 pin 12 C04 is 0v at switch on and 2.71v when the safety light goes solid amber. So I guess this is OK (voltage lower than the 2.8v you mentioned SVI2004)
I then measured all three pins of Q608 but I don't know which is which but going off the labels on the circuit board:
E is always 0v
the middle one with the semicircle is always 0v
B is 0v at switch on and 0.66v when safety light goes amber.
So am I right in thinking B looks normal, ie power from IC601, but one of the other pins should then emit a voltage to the coil but isn't?
I havnt removed anything so cant get at the pins for the relay so instead I measured either side of D603 and this was also 0v either side at all times suggesting to me the problem isn't the relay but something to do with Q608 either being faulty, or not enough voltage to switch it on? Where does it take it's power from to send a higher voltage signal to the relay?
(Oh and @ SVI2004, the serial number is FF4J23B221 and the number under the SVI 2004 by the right hand pin when looking from front is 16, if that's what you meant?)
IC601 pin 12 C04 is 0v at switch on and 2.71v when the safety light goes solid amber. So I guess this is OK (voltage lower than the 2.8v you mentioned SVI2004)
I then measured all three pins of Q608 but I don't know which is which but going off the labels on the circuit board:
E is always 0v
the middle one with the semicircle is always 0v
B is 0v at switch on and 0.66v when safety light goes amber.
So am I right in thinking B looks normal, ie power from IC601, but one of the other pins should then emit a voltage to the coil but isn't?
I havnt removed anything so cant get at the pins for the relay so instead I measured either side of D603 and this was also 0v either side at all times suggesting to me the problem isn't the relay but something to do with Q608 either being faulty, or not enough voltage to switch it on? Where does it take it's power from to send a higher voltage signal to the relay?
(Oh and @ SVI2004, the serial number is FF4J23B221 and the number under the SVI 2004 by the right hand pin when looking from front is 16, if that's what you meant?)
do you mean R630, the big one? both sides of that are also 0v at all times.
So do I have a rectifier issue? just to double check having no speakers connected would make no difference? im gonna plug one in just in case.....
Anyway, I think it looks like im getting no dc power from the rectifier and also therefore not to the SVI2004 pins that share it, as Ive noticed its not getting warm at all.
tomorrow Im gonna start at the top, with the transformer and impedance switch which looks to select 2 different voltages depending on it's setting. Illl see if that has AC there. then work back from there.
So do I have a rectifier issue? just to double check having no speakers connected would make no difference? im gonna plug one in just in case.....
Anyway, I think it looks like im getting no dc power from the rectifier and also therefore not to the SVI2004 pins that share it, as Ive noticed its not getting warm at all.
tomorrow Im gonna start at the top, with the transformer and impedance switch which looks to select 2 different voltages depending on it's setting. Illl see if that has AC there. then work back from there.
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thanks for that serial no. info! being into classic cars (hence the 4V8s username) its always nice to trace some history of them from VIN nos so didn't figure the same would be possible from old serial numbers.
I checked the pins 13 and 15 on the amp chip and also zero volts.
Checked ac outputs on the transformer and all good (38v, 32v and 11 ish).
those large capacitors are my suspect, but I just need to figure out of any of the transistors Q701 to Q705 and associated components in any way control whether there is the +-50v output from the rectifier or if they are unrelated and control other functions.
yes I'm getting into the swing of things, I studied electronic engineering back in my youth so its coming back to me now, and Im actually enjoying using the service manual to trace stuff and investigate what's going on
bed time now though
I checked the pins 13 and 15 on the amp chip and also zero volts.
Checked ac outputs on the transformer and all good (38v, 32v and 11 ish).
those large capacitors are my suspect, but I just need to figure out of any of the transistors Q701 to Q705 and associated components in any way control whether there is the +-50v output from the rectifier or if they are unrelated and control other functions.
yes I'm getting into the swing of things, I studied electronic engineering back in my youth so its coming back to me now, and Im actually enjoying using the service manual to trace stuff and investigate what's going on
bed time now though
So whilst at work today Ive done some more studying of the schematics in the service manual.
since I know I have correct AC from the transformer, and I know the functions coming from the 11.5v supply through the IC701 regulator are working OK, but that I dont have any output from the main rectifier (that provides +-50v) i was hoping it may be a simple case of bad ground connection as circled red. The ground is then traced highlighted yellow.
However since that also is used by IC701 (which is working) I think perhaps the ground must be OK but I will check it tonight.
So Im also then looking at the inputs/outputs from the speaker impedance selector switch. However it seems unlikely that more than one terminal would be faulty meaning no AC of either 32 or 38 gets through.
So then I think OK maybe D701 to D704 or C701 or C702 are likely culprits. However looking at the effects of a failure of any one of these seems to mean I would still get some form of DC output just lower voltage and less steady. Whereas I have zilch. So then I think perhaps the other capacitor C713 (which is present in my case) could possibly cause lack of AC to the rectifier if it was faulty and short circuited? Not really sure what it's for anyway.
So this is my train of thought at the moment and I will remove this main board tonight so I can test the points from the underside since I cant get at some of them from the top.
Question - when I remove the main board, should I do so leaving the heatsink arrangement all still attached to the SVI2004A? as I dont want to disturb it, however Im worried the weight etc will put stress on things?
since I know I have correct AC from the transformer, and I know the functions coming from the 11.5v supply through the IC701 regulator are working OK, but that I dont have any output from the main rectifier (that provides +-50v) i was hoping it may be a simple case of bad ground connection as circled red. The ground is then traced highlighted yellow.
However since that also is used by IC701 (which is working) I think perhaps the ground must be OK but I will check it tonight.
So Im also then looking at the inputs/outputs from the speaker impedance selector switch. However it seems unlikely that more than one terminal would be faulty meaning no AC of either 32 or 38 gets through.
So then I think OK maybe D701 to D704 or C701 or C702 are likely culprits. However looking at the effects of a failure of any one of these seems to mean I would still get some form of DC output just lower voltage and less steady. Whereas I have zilch. So then I think perhaps the other capacitor C713 (which is present in my case) could possibly cause lack of AC to the rectifier if it was faulty and short circuited? Not really sure what it's for anyway.
So this is my train of thought at the moment and I will remove this main board tonight so I can test the points from the underside since I cant get at some of them from the top.
Question - when I remove the main board, should I do so leaving the heatsink arrangement all still attached to the SVI2004A? as I dont want to disturb it, however Im worried the weight etc will put stress on things?
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It’ll be simplistic... tried using 4 ohm or 8 ohm mode... impedance sw may be it...
Check continuity from xfmr to rectifier.... diode test will quickly reveal rectifier health...
check continuity from rectifiers to caps... - there are a few jumper pins- it’s a long shot but could be dry joints...
It’s a simplistic circuit involved here... the answer is near.
Check continuity from xfmr to rectifier.... diode test will quickly reveal rectifier health...
check continuity from rectifiers to caps... - there are a few jumper pins- it’s a long shot but could be dry joints...
It’s a simplistic circuit involved here... the answer is near.
thanks yes I did try last night to measure for any voltage either side of all the rectifier diodes but I think they have a coating on the legs so got no reading. Or it could be I just realised I had my multimeter set on DC at that time but of course the inputs there would infact be AC, but continuity test is a good idea.
Hopefully tonight I'll suss it out and see what's needed to fix it
Hopefully tonight I'll suss it out and see what's needed to fix it
in my case Ive now got myself confused. I removed the bottom panel. testing continuity (power lead disconnected) I find that all wire inputs 701, 702, 703, 704 have continuity to each other and to ground and so do all connections on the transformer. this cant be right can it? so now I don't want to plug it back in incase something is shorted to ground somewhere......or is this normal that all windings eventually lead to ground and therefore each other? but resistance is also zero
I have also decided my impedence switch is suspect. Quite why it would be likely to fail I don't know since the number of times it will ever have been switched can probably be counted on one hand!
So aside from my last confused post (having googled how transformers work I think indeed all windings share a ground so probably nothing to worry about) I tested the output poles of the impedance switch relative to the switch position and the two sets of inputs. There was no continuity in either position but moving the switch slightly forward and back gave some intermittent continuity.
So I am now thinking this is likely the simple answer and I might just bypass it as I always will likely use the 8ohm setting.
Briedonis, when you say you cleaned yours, did you somehow take it apart? if so how and did you do that in situ or desolder it?
thanks
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