SX-1050 Blowing Fuses
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Stevesmullen
Well-Known Member
Im not sure if The fuses on the Power supply board are connected to the 8 Output transistors but they are very easy to test,they just unplug from the board and then you can easily test them for either shorts or open circuit with your DMM.And great advice from jblmar.
Im sure that someone with more expierence will chime in
Im sure that someone with more expierence will chime in
Stevesmullen
Well-Known Member
Do the 8 Output transistors test bad,do you know how to test them?
What l would do at this point is just go through the power supply board and test the Diodes and Caps and resistors to see if anything is bad,does anything look or smell fried?
I am not a tech just someone who is learning myself,but I would just go through and test what ever I could on my own when I was waiting for guidance from Markthefixer or EW.
If you dont have a copy of the service Manual be sure to down load it and then see if you can trace the path after the fuses that blew.
You do want to try to find the cause of failure before you put new fuses in,that normally just results in more smoke.
Was that you that won that SX-850 on Ebay?
What l would do at this point is just go through the power supply board and test the Diodes and Caps and resistors to see if anything is bad,does anything look or smell fried?
I am not a tech just someone who is learning myself,but I would just go through and test what ever I could on my own when I was waiting for guidance from Markthefixer or EW.
If you dont have a copy of the service Manual be sure to down load it and then see if you can trace the path after the fuses that blew.
You do want to try to find the cause of failure before you put new fuses in,that normally just results in more smoke.
Was that you that won that SX-850 on Ebay?
NO NO NO NO NO, STOP!!!!!! Please leave the innocent amp board alone!!! Please tell me you didn't unwrap the wire wraps....:tears:
EDIT: is this the same 1050 you posted about in march?
If you are popping BOTH fuses Fu1 and Fu2, you start ON the awr-104 board (the one with the fuses) testing diodes D2, D3, D4 & D5. Then you test C9 & C10 (470uF 80v) for shorts. It's probably one of the caps, shorted... (one fuse popping might mean a bad diode)
EDIT: perhaps pictures of the repair work in march are in order?
Since you called Fu1 and Fu2 by name, I assume you have the service manual? If not, download it.
To test the diodes, you will have to unsolder one lead on each diode, and then do the DMM diode test on each of them.
Then with the leads still disconnected, do an ohmmeter test on C9 & C10, and pay attention to the time it takes for each reading to increase as each capacitor is charged by the meter.
IF they ALL TEST OK, then reconnect everything.
Then you unsolder one leg each of R1 and R19 of the awr-103 board, which isolates the current draw off of the capacitors C9 & C10. Measure the ohms of both of the resistors (just in case, since they are isolated).
Then power it up and read the voltages (careful !! they are rather high) at pins 2 (+76v) and 3 (-76v) of the AWR-103 board (referenced to a metal chassis ground).
Hopefully before this point we will have had a discussion of where to get replacement parts and isolating R1 & R19 will be unnecessary.
tsd71
RIP Tom Petty
mark,i got this new board from someone who had a parts unit, i did notice one of the caps was loose from its solder when i was installing...i will go back and resolder the board and test the mentioned components...do you think the caps are bad or just need to be resoldered?i'll get back after testing and soldering
thanks
thanks
To be clear, this is a different awr-103 board.
You can test comparing to the OLD awr-103, as IT wasn't popping these fuses. You can also use it as a parts source, even though I would recommend new 470uf 80v caps.. these have been known as a source of long term trouble. IIRC we've been using 100v replacements...
Nope, the loose cap won't cause that, I'll bet the seller did that and knew/suspected there was a problem.
test test test.....
tsd71
RIP Tom Petty
ok i resoldered everything on the awr-104 board, powered up and guess what , no blown fuses...but now another problem,like i said earlier in my posts the first relay clicks just fine a few seconds after powering up...but the speaker relay is not opening up...i do notice a slight discoloration(burn) on that board(AWM-090) near D5-R25-R29-R28...could it be a bad transistor at Q7? anyway the unit is powered on all lights bright, no smoke or sparks,fm tuner is tuning in properly, all i need is the relay to click in and hopefully i have audio...
Go to the awr-103 board and read the regulated voltages.
The manual will help and this thread as well:
http://www.audiokarma.org/forums/showthread.php?t=124156
we fixed a power supply and extensively tested the amps.
it's worth reading... with schematics nearby to look back and forth to....
If the power supply regulated voltages are ok, then check the output voltages of the amp before the protection relay interrupts the circuit to the speakers.
IF the lamp fuse, if out, will prevent the relay from kicking in because the protect senses the lamp circuit's 8v AC for power on/off... it is the Fu5 1.5 amp fuse by the blue wire (in on pin 15 and out through pin 1) off by it's lonseome on the awr-104 board.
Re:at the awm-090 protection circuit, possibly, D5 & R25 forms a 33v 500mW zener voltage regulator and if bad WOULD upset the protection circuit. look for 33v at the point between D5 and R25, referenced to ground.
That area will run hot, Q7 runs saturated, but a 120v 100ma 1w npn hi-gain transistor will do.
This is the best: (mouser.com part number)
..... relay driver ............
522-ZTX1056A NPN TO-92E ebc 150v 3a 1w (Vce(sat)=0.3v @ 3a) 120mhz 30-1200 hfe
IF the 33v zener diode is misbehaving, there is a slightly different fix. Other very accomplished people on this board don't replace the 33v diodes directly, but rather use a 16v and a 17v zener in series. It's a bit of a push at 33v, especially at that power, so 2 diodes are more stable.
The manual will help and this thread as well:
http://www.audiokarma.org/forums/showthread.php?t=124156
we fixed a power supply and extensively tested the amps.
it's worth reading... with schematics nearby to look back and forth to....
If the power supply regulated voltages are ok, then check the output voltages of the amp before the protection relay interrupts the circuit to the speakers.
IF the lamp fuse, if out, will prevent the relay from kicking in because the protect senses the lamp circuit's 8v AC for power on/off... it is the Fu5 1.5 amp fuse by the blue wire (in on pin 15 and out through pin 1) off by it's lonseome on the awr-104 board.
Re:at the awm-090 protection circuit, possibly, D5 & R25 forms a 33v 500mW zener voltage regulator and if bad WOULD upset the protection circuit. look for 33v at the point between D5 and R25, referenced to ground.
That area will run hot, Q7 runs saturated, but a 120v 100ma 1w npn hi-gain transistor will do.
This is the best: (mouser.com part number)
..... relay driver ............
522-ZTX1056A NPN TO-92E ebc 150v 3a 1w (Vce(sat)=0.3v @ 3a) 120mhz 30-1200 hfe
IF the 33v zener diode is misbehaving, there is a slightly different fix. Other very accomplished people on this board don't replace the 33v diodes directly, but rather use a 16v and a 17v zener in series. It's a bit of a push at 33v, especially at that power, so 2 diodes are more stable.
tsd71
RIP Tom Petty
ok mark i have problems....i took readings off of awr-103 they are as follows
1. +24
2. +83
3. -57
4. g
5. +13
6. +13
7. -13
8. -44
9. -22
10. -20
11. -20
12. g
13. -6.3
14. -6.3
15. -0.9
16. -0.4
17. -0.4
18. -5.0
19. -5.0
i guess it looks like a awr-103 total rebuild....judging by the other thread you notated in your last post, this sounds similar
1. +24
2. +83
3. -57
4. g
5. +13
6. +13
7. -13
8. -44
9. -22
10. -20
11. -20
12. g
13. -6.3
14. -6.3
15. -0.9
16. -0.4
17. -0.4
18. -5.0
19. -5.0
i guess it looks like a awr-103 total rebuild....judging by the other thread you notated in your last post, this sounds similar
1. +24 +24v raw dc
2. +83 +76v raw dc
3. -57 -76v raw dc
4. g
5. +13 +13v regulated
6. +13 +13v regulated
7. -13 -13v zener diode
8. -44 -60v regulated possibly ok, the -57 may be too low?
9. -22 -30v regulated this is half of -44 and is ok
10. -20 -25v regulated resistor dropped from -30v this is also ok
11. -20 -25v regulated resistor dropped from -30v this is also ok
12. g
13. -6.3 +25v regulated resistor dropped from +30v
14. -6.3 +25v regulated resistor dropped from +30v
15. -0.9 +30v regulated
16. -0.4 +60v regulated
17. -0.4 +60v regulated
18. +5.0 +5.4v regulated
19. +5.0 +5.4v regulated
The -57 means that the caps on the awr-104 have to be looked at. Either the diodes D2 - D5 or the cap C10 470 uf 80v have a problem. The diodes are cheap, so when the caps are ordered, get the diodes too. The caps are axial leads, and get 100v caps (do C9 as well).
Once the -57 is back to -76, the -60v ( at -44) may come back. The -30 is supposed to be half of the -60, so -22 at half of -44 may be ok, and the -20 comes off of the -30 (at -22) so it too is probably ok.
The +60 is completely missing, so Q1 is definitely gone, while Q2 and Q3 are suspect (and cheap) and zener diode d1 is somewhat suspect, and at 5 cents is cheap insurance, so get one also. Get Q1, Q2, Q3 & D1.
The other parts numbers are easy to find in the other thread I mentioned, but these caps were harder to find in it:
the awr-104 board's caps c9 & c10 are:
mouser part # 140-HTRL100V470-RC 470uF 100v @ $1.34 ea in stock 105 degree c part ( get two, do them both )
IF they don't have that number, this will substitute:
mouser part # 140-XRL100V470-RC 470uF 100v @ $1.03 ea in stock 85 degree c part ( get two, do them both )
The awr-104 board's diodes D2 - D5 are 200v 1 amp general purpose, so go with mouser part # 512-1N4004 at $0.05 each.
2. +83 +76v raw dc
3. -57 -76v raw dc
4. g
5. +13 +13v regulated
6. +13 +13v regulated
7. -13 -13v zener diode
8. -44 -60v regulated possibly ok, the -57 may be too low?
9. -22 -30v regulated this is half of -44 and is ok
10. -20 -25v regulated resistor dropped from -30v this is also ok
11. -20 -25v regulated resistor dropped from -30v this is also ok
12. g
13. -6.3 +25v regulated resistor dropped from +30v
14. -6.3 +25v regulated resistor dropped from +30v
15. -0.9 +30v regulated
16. -0.4 +60v regulated
17. -0.4 +60v regulated
18. +5.0 +5.4v regulated
19. +5.0 +5.4v regulated
The -57 means that the caps on the awr-104 have to be looked at. Either the diodes D2 - D5 or the cap C10 470 uf 80v have a problem. The diodes are cheap, so when the caps are ordered, get the diodes too. The caps are axial leads, and get 100v caps (do C9 as well).
Once the -57 is back to -76, the -60v ( at -44) may come back. The -30 is supposed to be half of the -60, so -22 at half of -44 may be ok, and the -20 comes off of the -30 (at -22) so it too is probably ok.
The +60 is completely missing, so Q1 is definitely gone, while Q2 and Q3 are suspect (and cheap) and zener diode d1 is somewhat suspect, and at 5 cents is cheap insurance, so get one also. Get Q1, Q2, Q3 & D1.
The other parts numbers are easy to find in the other thread I mentioned, but these caps were harder to find in it:
the awr-104 board's caps c9 & c10 are:
mouser part # 140-HTRL100V470-RC 470uF 100v @ $1.34 ea in stock 105 degree c part ( get two, do them both )
IF they don't have that number, this will substitute:
mouser part # 140-XRL100V470-RC 470uF 100v @ $1.03 ea in stock 85 degree c part ( get two, do them both )
The awr-104 board's diodes D2 - D5 are 200v 1 amp general purpose, so go with mouser part # 512-1N4004 at $0.05 each.
tsd71
RIP Tom Petty
ok mark so i am ordering....
from the 104 board
d2 -# 512-1N4004
d5 -# 512-1N4004
c9 -# 140-HTRL100V470-RC
c10-# 140-HTRL100V470-RC
and the 103 board...
Q1 -# 512-ksc2073tu_q
Q2 -# 512-ksc2310ota
Q3 -# 512-ksc2310ota
D1 -# 512-1n5244b
i will order tonight , is there anything else i need before i put it in?
thanks very much appreciated
from the 104 board
d2 -# 512-1N4004
d5 -# 512-1N4004
c9 -# 140-HTRL100V470-RC
c10-# 140-HTRL100V470-RC
and the 103 board...
Q1 -# 512-ksc2073tu_q
Q2 -# 512-ksc2310ota
Q3 -# 512-ksc2310ota
D1 -# 512-1n5244b
i will order tonight , is there anything else i need before i put it in?
thanks very much appreciated
d2 d3 d4 d5, at least 4 of them not 2
as for anything else, I had been thinking about that...
it would be a good idea to replace the other caps on the awr-103 board,
and since we are not sure the negative regulator IS ok, and because the replacement parts are FAR cheaper than postage/shipping, get the rest of the transistors with these exceptions : only two 2073's instead of three
and to mount Q1 get either:
532-249 1 oz thermal compound $4.71
or
526-NTE303 1 gram thermal compound $1.77
I'm NOT sure if 1 gram is enough for more than 1 power transistor.
and before replacing q1, I have to warn you about the mica insulator partially camoflaged by the thermal grease....
it's fragile...
a spare would be a good idea too: 534-4673 to-220 mica insulator $0.14
tsd71
RIP Tom Petty
mark, any resistors that i should order for the 103 board before i send in the order, i've put together my order sheet and included 1or 2 extra of everything just in case
i'm replacing all the caps on the 103, also all the transistors, and diodes as well,how about C11 and C21 the ceramic caps, do these need replacing too?
thanks again
tim
i'm replacing all the caps on the 103, also all the transistors, and diodes as well,how about C11 and C21 the ceramic caps, do these need replacing too?
thanks again
tim
Just electrolytic caps (and tantalum caps, but there aren't any here) the ceramics really don't have a failure mode (other than being physically destroyed).
Check the two 10 ohm resistors R1 ad R19. They should be ok, but.....
tsd71
RIP Tom Petty
parts are in for the 1050, i will start getting to it later today, i will keep you posted...by the way my neighbor had a sx-1250 in the garage, got it for 25.00,musty dusty but very nice and very heavy....this is my next project...plugged it in, nothing, checked the fuses, no fuses, replaced all the fuses, clicked the on switch and the (R1)wire wound 20w 3.3ohm resistor(ACN-003) on the power board is smoking, it's attached to the microtemp(AEX-005) with a twist tie...now what???
The output transistors are shorted. Don't turn it on.....
But the 1250 is a whole nuther project.. and with ALL the fuses removed, I think the previous owner KNEW something (and it's NOT good)
There are 4 per side on the heatsinks. They are the oval metal cans.
But there are connectors on the 1250 that can be disconnected to isolate the amplifiers AND the power circuits for BOTH channels at the transformer, before the rectifiers.... (on the protection and power supply catds - the metal straps)
so do nothing for now except download the service manual and study it, while looking at the insides of the 1250, so you "get the lay of the land".
although i'm wondering if you are pressing your luck on this one.