Just to confirm with V9 Adjustment. I will do the following
1. turn VR701 clockwise completely
2. connect TP703 to chasis and resistors to speaker terminals
3. Volume at 0
4. main speaker on
5. straight dc
6. Fire up amp
7 Adjust VR702 to -0.1V (DC)
8 Adjust VR701 to 0V (DC)
9. Power off
disconnect earth and TP703
* fire back up, should be good to go with luck *
1. turn VR701 clockwise completely
2. connect TP703 to chasis and resistors to speaker terminals
3. Volume at 0
4. main speaker on
5. straight dc
6. Fire up amp
7 Adjust VR702 to -0.1V (DC)
8 Adjust VR701 to 0V (DC)
9. Power off
disconnect earth and TP703
* fire back up, should be good to go with luck *
An externally hosted image should be here but it was not working when we last tested it.
Hi Ray and all
My DC range seems to be only 200v or 500v. I looking for low readings of 0.1v and 0v. maybe this meter is not up to it
V9 Technics speaker impedance circuit opamp change
Hello,
I have on hand 3 OPA1642s. LM4562s 6 of them
My Technics SU-V9 is having relay issues, and needs a recap, and possible opamp change. The currenty is AN6552. I can get an soic adapter for the OPA1642 or any other opamp There is only 6 caps - 2 elect, 3 film 1 ceramic
The didode near the relay - measures 608 and other direction 1010 (still in the pcb), others were 1 in one direction and 500 something the other direction
I took a screen shot of the AN6552 in the speaker circuit.
Thank you
Best Regards
Sam
Hello,
I have on hand 3 OPA1642s. LM4562s 6 of them
My Technics SU-V9 is having relay issues, and needs a recap, and possible opamp change. The currenty is AN6552. I can get an soic adapter for the OPA1642 or any other opamp There is only 6 caps - 2 elect, 3 film 1 ceramic
The didode near the relay - measures 608 and other direction 1010 (still in the pcb), others were 1 in one direction and 500 something the other direction
I took a screen shot of the AN6552 in the speaker circuit.
An externally hosted image should be here but it was not working when we last tested it.
Thank you
Best Regards
Sam
Panasonic - datasheet pdf
AN4558 is same as AN6552
TheAN4558 (AN6552) andthe AN4558S (AN6552S)
are dual operational amplifiers with phase compensation
circuits built-in, and suitable for application to various
electronic circuits such as active filters and audio pream-
plifiers.
n
Features
• Phase compensation circuit
• High voltage gain, low noise
• Output short-circuit protection
• Slew rate:SR=1V/
AN4558 is same as AN6552
TheAN4558 (AN6552) andthe AN4558S (AN6552S)
are dual operational amplifiers with phase compensation
circuits built-in, and suitable for application to various
electronic circuits such as active filters and audio pream-
plifiers.
n
Features
• Phase compensation circuit
• High voltage gain, low noise
• Output short-circuit protection
• Slew rate:SR=1V/
Technics SU-V9 replacement Thyristors
The old part I can not find, but without the all the code from the service manual i managed to sort out it was a Mitsubishi part : CR6AM-4
PDF for the Mitsu part
(Datasheet) CR6AM PDF - Mitsubishi : Thyristor (1-page)
Mouser link for what appears to be close to the original? I think but not sure.
MCR218-4G Littelfuse | Mouser Australia
The Power Circuit Q601-4
The old part I can not find, but without the all the code from the service manual i managed to sort out it was a Mitsubishi part : CR6AM-4
PDF for the Mitsu part
(Datasheet) CR6AM PDF - Mitsubishi : Thyristor (1-page)
Mouser link for what appears to be close to the original? I think but not sure.
MCR218-4G Littelfuse | Mouser Australia
The Power Circuit Q601-4
I have serviced Technics SU-V9s for years and never had a faulty control thyristor.
I would say most of the BT152 range will be fine. Nothing special required and plenty of current available to drive 35mA.
BT152-600R | NXP, BT152-600R, Thyristor, 650V 13A, 32mA 3-Pin, TO-220AB | WeEn Semiconductors Co., Ltd
I would say most of the BT152 range will be fine. Nothing special required and plenty of current available to drive 35mA.
BT152-600R | NXP, BT152-600R, Thyristor, 650V 13A, 32mA 3-Pin, TO-220AB | WeEn Semiconductors Co., Ltd
Thank you Mona. I am not sure i can see that part of Mouser RS or Digikey
Thank you Jon.
Here is the story behind the V9, my brothers went on about the smell from it ( common with that age as same year tuner is the same), anyway to the point, i put it on a box with bicarb vinegar and paper.
Since then ive had a bit of trouble with it, first relay wasnt clicking on, sometimes it would work, a friend had me read underneath, I was only getting 29v 31v on Q601-4 instead of 54v. I redid the power lines on, went to do a reading and blew a pin on Q604, hence the replacement.
That part looks good and RS has free ship in Australia. 13A will be fine? ive seen UK plugs with 13A fuses. I think i went looking to match the specs, so couldnt widen my field
'Seems that grandma's "bicarb and vinegar" treatment did some damage or likely, the age of the unit is telling you that parts are deteriorating anyway. The cat pee smell is of course, the urea resin binder in the paper PCBs breaking down. It doesn't stop with deodorizing though - that just continues at a steady rate, depending somewhat on temperature inside the case. I have an SUV50 that sees little use and is bit younger but I've had to recap it even though the PCB is still almost odourless. Your problem could be the result of a harder working life or even a different PCB supplier quality.
Frankly, I wouldn't expose electronic assemblies to acetic acid (vinegar) or the acetate solution vapours you wind up with. It may dispel any lingering odours in the short term but if it doesn't also initiate corrosion of clean copper and alloy contact surfaces, it will at least speed up any ongoing process.
Some years back, I read a thread here where the OP finally, after lacquering the boards in his old amplifier, reduced the stench and stopped blaming the cat. Not sure how it is now though
Frankly, I wouldn't expose electronic assemblies to acetic acid (vinegar) or the acetate solution vapours you wind up with. It may dispel any lingering odours in the short term but if it doesn't also initiate corrosion of clean copper and alloy contact surfaces, it will at least speed up any ongoing process.
Some years back, I read a thread here where the OP finally, after lacquering the boards in his old amplifier, reduced the stench and stopped blaming the cat. Not sure how it is now though
Hi Ian,
I bought the V9 in a non working state, though it was only due to controls being dirty. I do worry the bicarb and vinegar has done some damage, but lying in bed thinking about it, there was an issue with the relay not clicking on early before this , but now it is much worse, before i could fix it. I just worry why power is not getting through 29v vs 54v it should be. Also noticed a 0.047uf cap,the leg rejoined couldve broken, replace it with a new one., smell is bad but is in the largest room close to the sliding doors
, all that cleaning still the same once things heat up here in Queensland
I bought the V9 in a non working state, though it was only due to controls being dirty. I do worry the bicarb and vinegar has done some damage, but lying in bed thinking about it, there was an issue with the relay not clicking on early before this , but now it is much worse, before i could fix it. I just worry why power is not getting through 29v vs 54v it should be. Also noticed a 0.047uf cap,the leg rejoined couldve broken, replace it with a new one., smell is bad but is in the largest room close to the sliding doors
, all that cleaning still the same once things heat up here in Queensland
Yes, warmer climates are hard on electronics - I had a relative who was a repair tech. on the Sunshine Coast where the higher temperatures plus salt air were a big problem for increasingly complex and finer boards, switches and connectors, going back many years.
Most Technics SE and SU series models were based on Sandman's class S feed-forward operating principle but this was dumbed down over the long life of the series, presumably for cost and reliability reasons, though most of them still had a resistive bridge-balanced output stage in some form, where a class B power amplifier augmented the output of a small class A amp, in the manner of Quad's "current dumping" designs but operating on Sandman's class S principle, which used a resistive rather than reactance balance bridge. This was shown by JLH in his published rundown of the SE-A100 model. If you were looking to fix a regular class AB amplifier here, you won't find one, since this is a weird science model.
Aside from the unusual operating principle, there is a TA7317 protection IC in there and these have small caps which always seem prone to failure, resulting in erratic or non-operation of the protection relay. I'd replace all the caps associated with it. I'd also pull, clean the surfaces and refit the many connectors apparently in there too.These may not be a fixes but will reduce the likely number of faults.
Most Technics SE and SU series models were based on Sandman's class S feed-forward operating principle but this was dumbed down over the long life of the series, presumably for cost and reliability reasons, though most of them still had a resistive bridge-balanced output stage in some form, where a class B power amplifier augmented the output of a small class A amp, in the manner of Quad's "current dumping" designs but operating on Sandman's class S principle, which used a resistive rather than reactance balance bridge. This was shown by JLH in his published rundown of the SE-A100 model. If you were looking to fix a regular class AB amplifier here, you won't find one, since this is a weird science model.
Aside from the unusual operating principle, there is a TA7317 protection IC in there and these have small caps which always seem prone to failure, resulting in erratic or non-operation of the protection relay. I'd replace all the caps associated with it. I'd also pull, clean the surfaces and refit the many connectors apparently in there too.These may not be a fixes but will reduce the likely number of faults.
I missed a few details above that might be helpful to others too. Here is a short rundown on the operating principle, though the model discussed is further up in the stratosphere of performance and price: Technics SE-A100 Class AA Power Amplifier - Amplifiers & Pre-Amps - StereoNET
The front panel of my model sports an LED indicator that shows when DC balance of voltage amplifier (class A) is stable at zero potential and the relay then switches in the power amplifier by powering the output relay. I assume it is similar with your model. In practice, this should appear to be little different to the normal power-up delay that prevents speaker thumps with most audio amplifiers but the purpose is quite different and if the amplifier won't consistently switch to the powered-up state, it could well spell trouble with either the class A or B amplifiers in either channel. You could isolate one channel, disconnect speakers etc. to check where the problem lies before diving into shallow water. Take care.
The front panel of my model sports an LED indicator that shows when DC balance of voltage amplifier (class A) is stable at zero potential and the relay then switches in the power amplifier by powering the output relay. I assume it is similar with your model. In practice, this should appear to be little different to the normal power-up delay that prevents speaker thumps with most audio amplifiers but the purpose is quite different and if the amplifier won't consistently switch to the powered-up state, it could well spell trouble with either the class A or B amplifiers in either channel. You could isolate one channel, disconnect speakers etc. to check where the problem lies before diving into shallow water. Take care.
Hi Ian
That was an interesting read. The Technics class A amps run rather warm.
Yes, rather warm and humid a bit today. I do cover my Technics collection when not in use with sheets. The sheet was also good for the V9 and kept her odour trapped in.
I found hidden partially from sight due to the cabinet a dry joint on cap C803. I think recapping and cleaning will help. I redid the connectors sometime back. I took out the relay? not sure if the contacts are dirty, but if C803 was the issue I will know once I get the thyristors.
To make a better earth maybe tire J801 and earth 803 together. I re did the power lines in
That was an interesting read. The Technics class A amps run rather warm.
Yes, rather warm and humid a bit today. I do cover my Technics collection when not in use with sheets. The sheet was also good for the V9 and kept her odour trapped in.
I found hidden partially from sight due to the cabinet a dry joint on cap C803. I think recapping and cleaning will help. I redid the connectors sometime back. I took out the relay? not sure if the contacts are dirty, but if C803 was the issue I will know once I get the thyristors.
To make a better earth maybe tire J801 and earth 803 together. I re did the power lines in
Technics SU-V9 - caps
Happy New Year
Thank you in advance the help.
I have just found a few bad caps in my tuner, and not sure with my V9 yet as i am waiting on some thyristors to arrive ( i blew up one testing.
What is the general good capacitor for small values 100uf 33uf 3.3uf on the main board of amplifers, i would expect long live kinds like FM or FR (appears to be new). I do think any are in line of the audio signal - maybe low esr which seems the choice on DIY audio.
thank you
Sam
Happy New Year
Thank you in advance the help.
I have just found a few bad caps in my tuner, and not sure with my V9 yet as i am waiting on some thyristors to arrive ( i blew up one
testing.What is the general good capacitor for small values 100uf 33uf 3.3uf on the main board of amplifers, i would expect long live kinds like FM or FR (appears to be new). I do think any are in line of the audio signal - maybe low esr which seems the choice on DIY audio.
An externally hosted image should be here but it was not working when we last tested it.
thank you
Sam
Last edited:
Look for polarization - if there is no indication on the cap, PCB or schematic, audio coupling caps could be special non-polarized types which won't be stocked locally. Low ESR is not necessary for coupling - it's desirable for most other small cap. applications in audio though. Panasonic FC, FM are fine and you don't need the super low ESR for SMPS applications that FR grade is intended for.
Regarding your tuner - be very careful what caps you touch in there and of course, only the few electrolytics may need replacement. If you remove or even touch anything from the actual FM and AM tuner sections though, you may well affect or completely detune the critical sections that detect and demodulate the signal or even the stereo separation circuitry. Then you'll need an RF expert to get it to work properly again. Without knowing what it is, I'm guessing it is a similar vintage to your amplifier - early 1980s and probably before microprocessors were common. If it has the old mechanical (rotary capacitors) tuning with slide-rule dial and cord, that identifies the sections to stay away from.
Regarding your tuner - be very careful what caps you touch in there and of course, only the few electrolytics may need replacement. If you remove or even touch anything from the actual FM and AM tuner sections though, you may well affect or completely detune the critical sections that detect and demodulate the signal or even the stereo separation circuitry. Then you'll need an RF expert to get it to work properly again. Without knowing what it is, I'm guessing it is a similar vintage to your amplifier - early 1980s and probably before microprocessors were common. If it has the old mechanical (rotary capacitors) tuning with slide-rule dial and cord, that identifies the sections to stay away from.
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