schematic of your amplifier has been a problem to locate ...i ve been checking though some other similar models of the same time and it seems that in the secondary power supply there is either a fuse or a fuse resistor if its a resistor it should be 4.7 R and coloured from left to right yellow -purple - and 2 stripes of gold or silver
check on this with reference to ground to see if voltage comes in and out of it .... in the closest schematic te above was named R406 and R407 for plus and minus...
check on this with reference to ground to see if voltage comes in and out of it .... in the closest schematic te above was named R406 and R407 for plus and minus...
there is a remote posibility that these are not transitors on the regulator area but are simple regulators in this case in the negative regulator and always with reference to ground you need to measure
pin 1:-0.6 volts
pin 2: -17.2 volts
and pin 3:-9.8 volts
most imprtand is to see that the input of the regulator has the -17.2 volts ...if not replace fuse 804 or a part that is named ICP 801 ...the above is a special type of fuse but you may as well replace it with any normal fuse rated from 2.5 to 3A
here is a related schematic
pin 1:-0.6 volts
pin 2: -17.2 volts
and pin 3:-9.8 volts
most imprtand is to see that the input of the regulator has the -17.2 volts ...if not replace fuse 804 or a part that is named ICP 801 ...the above is a special type of fuse but you may as well replace it with any normal fuse rated from 2.5 to 3A
here is a related schematic
Attachments
Mooly:
It is marked 7909. There is no short between any of its legs. The two resistors next to the 4 diodes read ~5.2Ohm each.
Sakis:
ICP801 is one of the two resistors measuring 5.2Ohms that Mooly had me measure... next to the four diodes.
7909 - IC801 reads:
Pin 1: +0.60v
Pin 2: -17.64V
Pin 3: -0.16V
It seems strange that pin 1 is POSITIVE 0.6v and not negative... Could this be the issue? Or maybe the 7907/IC801 is fried?
Out of curiosity Sakis does secondary power supply refer to the 9v system where the main transformer connects to, or the stuff on what I have been calling the "Aux" board with the small xformer?
Thanks guys!
And super thanks for getting the schematic. Kudos to you.
EDIT: Sorry I think I got my pin numbers reversed as far as 1 and 3 go.
I think Pin 1 is actually -0.03v or so and pin 3 is +0.74v after retesting. The striped side of D806 matches -.03v and the unstribed side reads 0v.
Seems the pin 1 voltage is low... should be -0.60v and its near 0v in this test, was -0.16v before.
It is marked 7909. There is no short between any of its legs. The two resistors next to the 4 diodes read ~5.2Ohm each.
Sakis:
ICP801 is one of the two resistors measuring 5.2Ohms that Mooly had me measure... next to the four diodes.
7909 - IC801 reads:
Pin 1: +0.60v
Pin 2: -17.64V
Pin 3: -0.16V
It seems strange that pin 1 is POSITIVE 0.6v and not negative... Could this be the issue? Or maybe the 7907/IC801 is fried?
Out of curiosity Sakis does secondary power supply refer to the 9v system where the main transformer connects to, or the stuff on what I have been calling the "Aux" board with the small xformer?
Thanks guys!
And super thanks for getting the schematic. Kudos to you.
EDIT: Sorry I think I got my pin numbers reversed as far as 1 and 3 go.
I think Pin 1 is actually -0.03v or so and pin 3 is +0.74v after retesting. The striped side of D806 matches -.03v and the unstribed side reads 0v.
Seems the pin 1 voltage is low... should be -0.60v and its near 0v in this test, was -0.16v before.
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It isn't a concern that the voltage of pin 1 is -0.03v to -0.16v instead of -0.60v? Should I be replacing the same regulator on the +9V side for consistencies sake? Thanks!
By the way, IC800 on my board is numbered 7809 not 7812 as indicated by that schematic.
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Okay thanks! Should I replace the 7809 as well? Is any 7909 okay or are some better than others? Thanks!
That's useful Sakis 
looks very similar.
Just replace the reg -17 volts in and nothing out = duff
Any marked 7909 type will be OK... however it's not the most common value around so if you struggle to find one locally get a 7905 and a small wattage 4.7 volt zener and you can "make" a 7909 by adding the zener to the ground connection replacing the diode already there. Make sure it's a 79 not 78 when you buy.
Now if it were me I might look to replace the caps that feed those regs, that's the electroylitics near the regs C804 and C805. Wonder if it runs a bit hot around there.
looks very similar. Just replace the reg -17 volts in and nothing out = duff
Any marked 7909 type will be OK... however it's not the most common value around so if you struggle to find one locally get a 7905 and a small wattage 4.7 volt zener and you can "make" a 7909 by adding the zener to the ground connection replacing the diode already there. Make sure it's a 79 not 78 when you buy.
Now if it were me I might look to replace the caps that feed those regs, that's the electroylitics near the regs C804 and C805. Wonder if it runs a bit hot around there.
well in all these repair years ( over 30 ) never had to replace a regulator in all my life ...may be one or two ...i am pretty sure that from two the one should be on a tv and not an amplifier
i am pretty sure that this might be a soldering issue but this is for the OP to find .... at least an 7909 cost next to nothing so trying will not be costly ...
lets see how the forum/thread/post/telerepair will work out ha ha ha ha
i am pretty sure that this might be a soldering issue but this is for the OP to find .... at least an 7909 cost next to nothing so trying will not be costly ...
lets see how the forum/thread/post/telerepair will work out ha ha ha ha
Got a LM7909CT on order from Digikey right now. Why would you replace those caps out of curiosity, would any old electrolytic of the same value be a fine match?
BTW Sakis, I resoldered the 7909 since it was cracking at the bottom... probably from me moving it so much to get a read. Same result though, no good. Will let you guys know what happens.
BTW Sakis, I resoldered the 7909 since it was cracking at the bottom... probably from me moving it so much to get a read. Same result though, no good. Will let you guys know what happens.
electrolytics fails under stress of opetration heat and time ....so called solid state equipment actually doesnt exist ...any device that has electrolytics inside some time will fail .... may be from quality of parts and quality of design this will happen after 20-30 years but the truth is that eventually will fail
power supply caps will fail easier since are stressed more for sure the ones that operate in non switching applications will last longer
power supply caps will fail easier since are stressed more for sure the ones that operate in non switching applications will last longer
Electroylitics are the number one failure item in most commercial equipment, particularly switch mode power supplies where they are highly stressed.
Having spent many years as a bench engineer in the electronics repair trade you develop a second sense for where the trouble is and what caused it... to many hours spent chained to the soldering iron
I always use a 'scope for checking DC voltages as it instantly shows up problems like failing caps, the DC voltage might read OK but there could be several volts of ripple superimposed on it too.
Let us know how you get on... and when you first power it up make sure the new reg doesn't overheat... if it does something else is wrong. And check the soldering on the other 7809 too but don't at this stage resolder everything in sight as the chance of you putting a short or blob of solder might be a little high, by all means look and correct anthing obvious but that's all ... not that we are casting aspertions on your soldering skills... just work on one issue at once. It's too easy to inadvertently put another problem on the unit.
Having spent many years as a bench engineer in the electronics repair trade you develop a second sense for where the trouble is and what caused it... to many hours spent chained to the soldering iron
I always use a 'scope for checking DC voltages as it instantly shows up problems like failing caps, the DC voltage might read OK but there could be several volts of ripple superimposed on it too.
Let us know how you get on... and when you first power it up make sure the new reg doesn't overheat... if it does something else is wrong. And check the soldering on the other 7809 too but don't at this stage resolder everything in sight as the chance of you putting a short or blob of solder might be a little high, by all means look and correct anthing obvious but that's all ... not that we are casting aspertions on your soldering skills
... just work on one issue at once. It's too easy to inadvertently put another problem on the unit.
Sakis, regulators can fail... I had a defective 78M24 in a Marantz PM-35 amp that I got non-working from Freecycle... other than some cracked solder joints it was the only fault. It would sometimes work too, which was strange, but it ran really hot. The replacement 7824 that I fitted however runs cool - strange!
While I am waiting for the 7909 to come in, I was thinking about replacing those two caps that feed the reg's C804/C805... They read 1000uF and 25V. Should I replace them with any aluminum cap of the same value, or should I be looking for something special. I noticed there are some 10000hr vs 2000hr caps etc... I'd probably look to get the longer life, but besides that?
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P13121-ND
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P13121-ND
The first thing to check is the physical size and the lead spacing or pitch. Any parts replaced IMO have to look just like factory fit.
The life of the caps is often quoted at the max ripple current and temperatures... so 2000 hours becomes many many times longer in more "normal" use. That said the 105 degree parts are usually preferred over 85 degree.
You can go higher on the voltage rating as long as it fits, so 35 or 63 volt types are OK.
The ones in your link look fine.
The life of the caps is often quoted at the max ripple current and temperatures... so 2000 hours becomes many many times longer in more "normal" use. That said the 105 degree parts are usually preferred over 85 degree.
You can go higher on the voltage rating as long as it fits, so 35 or 63 volt types are OK.
The ones in your link look fine.
before replacing and that will be short of un upgrade thing.... it will be wise to check if any of these caps had drifted from original value ( can be easilly done with a capacitor meter even the ones with 15 USD that will not be acurate but at least provide an indication of the situation )
the point is that capacitor failures are epidemic meaning if one is drifted or leacky expect more if not all ....
the point is that capacitor failures are epidemic meaning if one is drifted or leacky expect more if not all ....
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