Hi all.
I am looking for the service manual for a Sony receiver, STR-V2 (mid 70s). Nothing anywhere, including Hifi Engine--apart from a document desrcribing the whole series' tuner alignment etc., without overall schematics. This document does mention that the STR-V2 is an outlier in the STR-Vx lineup, hence my problem!
It was working fine until yesterday, when I moved it to my basement shop. Now it instantly blows fuses in one of the AC low voltage legs (i.e. after transformer). Is it a failed capacitor (failed closed circuit)? A failed voltage regulator transistor (if any)? Problem is I have no schematics to suggest a culprit...
As I wrote, service manuals for other receivers in the same series are available, but the STR-V2 is different from the others. Tone controls are in power amplifier feedback loop, it has no preamplifier stage! I know it was almost bottom-of-the-line originally, but I like its sound in my 'retro' setup. Very 70s, a bit of emphasis on bass.
Please help me... Cheers!
--Christian
I am looking for the service manual for a Sony receiver, STR-V2 (mid 70s). Nothing anywhere, including Hifi Engine--apart from a document desrcribing the whole series' tuner alignment etc., without overall schematics. This document does mention that the STR-V2 is an outlier in the STR-Vx lineup, hence my problem!
It was working fine until yesterday, when I moved it to my basement shop. Now it instantly blows fuses in one of the AC low voltage legs (i.e. after transformer). Is it a failed capacitor (failed closed circuit)? A failed voltage regulator transistor (if any)? Problem is I have no schematics to suggest a culprit...
As I wrote, service manuals for other receivers in the same series are available, but the STR-V2 is different from the others. Tone controls are in power amplifier feedback loop, it has no preamplifier stage! I know it was almost bottom-of-the-line originally, but I like its sound in my 'retro' setup. Very 70s, a bit of emphasis on bass.
Please help me... Cheers!
--Christian
Thanks! Unfortunately this is the document without overall schematics I was referring to above ("apart from a document desrcribing the whole series' tuner alignment etc.").
--Christian
Cool. I am more familiar with 60s-70s receivers, with separate preamp and amp sections, and tone controls in preamp or just after preamp.
Was switching from preamp-power amp configuration to only power amp configuration a common thing for manufacturers to do after the 70s? The STR-V45 (1980) had a 'tone control' amp separate from the powe amp. Not discrete, though: opamps. Cheers!
--Christian
Don't need a plan. All the same. *Rectifier*, then capacitor(s).
FIRST use a Lamp (Dim Bulb) Limiter.
Disconnect things. Take the rectifier right out. Is it still shorted? Then look for scrap-metal fallen in (stuff happens). If OK that way, just replace the rectifier (they are cheap now) with something at least as big and twice the voltage of the next capacitor. But first look for Ohms across the next cap(s). Normal is to start low and go to several K ohms. Steady zero ohms is a short. Take the cap out and try again to see if the short is really downstream.
Thanks!
A failed diode? Or capacitor. There is no sign of heat damage. I'll check. I can of course troubleshoot it, eventually, but I put the cover back on. A schematics seemed like something I'd like to have... It only has sentimental value, as I found the receiver in question on the sidewalk a number of years ago, thrown away by stupid neighbours. Cheers!
--Christian
A failed diode? Or capacitor. There is no sign of heat damage. I'll check. I can of course troubleshoot it, eventually, but I put the cover back on. A schematics seemed like something I'd like to have... It only has sentimental value, as I found the receiver in question on the sidewalk a number of years ago, thrown away by stupid neighbours. Cheers!
--Christian
There is a service manual on EBay at this time. I'd recommend getting it since it has information you'll need.
I have one of these on my bench that did the same thing. The issue with mine is two shorted output transistors on one channel and a shorted diode in the rectifier. (Power supply board and amplifier board.) The question as to which came first is unknown. But oddly mine appears to have had the same issue with the other channel in it's past. The tech replaced the other two output transistors and one diode in the rectifier.
The unit has, originally, four 1N4003 diodes in the rectifier which is too weak imho (200V@1A.) Use either 1N4007s (1kv@1A) or as I did, drill the holes slightly larger and use 1N5408's (1kv@3A) to get better current handling matching closer to the 3.15A and 1.6A AGC fuses. (Fuse needs to blow before a component does.)
Use a dim bulb tester to protect the two AGC fuses otherwise you'll keep blowing one or both until you find the short. Note the 1.6A fuse is for the lights and the 3.15A fuse is for the rest of the unit.
Use a multimeter in diode check to test the diodes for shorts and each of the transistors. Lift the leads and recheck to confirm.
I tested the ele. caps in mine and found they were ok for test purposes but should be replaced anyway due to age and tolerance.
For the transistors, note one is used on the power supply as well (2SC1826) so you have three 2SC1826 (NPN) and two 2SA768 (PNP) in total to check at a minimum. Check the other diodes and transistors in the circuit path for shorts once you find one that fails. These transistors are obsolete now so you would need to find a replacement. I found a few options:
Sanken NPN 2SC1826
MJE15030
TIP41(C, D, E, or F)
KSD1526 (O or Y)
Sanken PNP 2SA768
MJE15031
TIP42 (C, D, E, or F)
KSB596 (O or Y)
I went with the MJE's due to availability but the specs are all different so expect some adjustments which is why you need the service manual.
Note these power amp transistors have driver transistors as well that should be checked:
NPN 2SD667
KSC2383Y
KSC2316
PNP 2SB647
KSA1013Y
KSA916
Right now I'm focusing on the power board and amplifier board.
Chris
I have one of these on my bench that did the same thing. The issue with mine is two shorted output transistors on one channel and a shorted diode in the rectifier. (Power supply board and amplifier board.) The question as to which came first is unknown. But oddly mine appears to have had the same issue with the other channel in it's past. The tech replaced the other two output transistors and one diode in the rectifier.
The unit has, originally, four 1N4003 diodes in the rectifier which is too weak imho (200V@1A.) Use either 1N4007s (1kv@1A) or as I did, drill the holes slightly larger and use 1N5408's (1kv@3A) to get better current handling matching closer to the 3.15A and 1.6A AGC fuses. (Fuse needs to blow before a component does.)
Use a dim bulb tester to protect the two AGC fuses otherwise you'll keep blowing one or both until you find the short. Note the 1.6A fuse is for the lights and the 3.15A fuse is for the rest of the unit.
Use a multimeter in diode check to test the diodes for shorts and each of the transistors. Lift the leads and recheck to confirm.
I tested the ele. caps in mine and found they were ok for test purposes but should be replaced anyway due to age and tolerance.
For the transistors, note one is used on the power supply as well (2SC1826) so you have three 2SC1826 (NPN) and two 2SA768 (PNP) in total to check at a minimum. Check the other diodes and transistors in the circuit path for shorts once you find one that fails. These transistors are obsolete now so you would need to find a replacement. I found a few options:
Sanken NPN 2SC1826
MJE15030
TIP41(C, D, E, or F)
KSD1526 (O or Y)
Sanken PNP 2SA768
MJE15031
TIP42 (C, D, E, or F)
KSB596 (O or Y)
I went with the MJE's due to availability but the specs are all different so expect some adjustments which is why you need the service manual.
Note these power amp transistors have driver transistors as well that should be checked:
NPN 2SD667
KSC2383Y
KSC2316
PNP 2SB647
KSA1013Y
KSA916
Right now I'm focusing on the power board and amplifier board.
Chris