Hi. Hope you are all well.
My Technics SUV5 has an issue. I would be grateful if you can help. Relay will not come on for 5- 10 mins after switch on. Either a failing cap or transistor or cold solder. Resoldered relay but no change and some wires that had been previously replaced, When relay does come on it scrapes and struggles to click. Once running it is fine and relay switches on and off nicely with speaker selection. Voltage at relay is 50 v with relay off but once running 25v.
Best Wishes
My Technics SUV5 has an issue. I would be grateful if you can help. Relay will not come on for 5- 10 mins after switch on. Either a failing cap or transistor or cold solder. Resoldered relay but no change and some wires that had been previously replaced, When relay does come on it scrapes and struggles to click. Once running it is fine and relay switches on and off nicely with speaker selection. Voltage at relay is 50 v with relay off but once running 25v.
Best Wishes
Just in case it help somebody. Fixed it. I thought it would be a fault with the dc protection circuit itself as the amp has very low dc of under 2mv on each channel. With help I previously fixed another technics amp with such an issue.
Looking at circuit diagram all wires lead to the speaker selector (so to speak) as relay switches on and off when you switch speakers. Turned out to be loose solder on wires on speaker selector. Reflowed with a bit of extra solder and all is well........ I hope.
Looking at circuit diagram all wires lead to the speaker selector (so to speak) as relay switches on and off when you switch speakers. Turned out to be loose solder on wires on speaker selector. Reflowed with a bit of extra solder and all is well........ I hope.
Hi. That was not it. Also replaced relay and still same issue. AMP ok for 2-3 days after switch off but realy struggles after that for a few mins. So probably a failing transistor or resisitor in protection circuit but not sure which. Any help would be great.
Hard to diagnose as it taked 2 -3 days of non use to malfunction!
Thanks
Hard to diagnose as it taked 2 -3 days of non use to malfunction!
Thanks
As usual:
- replace electrolytic caps as these are often worn out in 1981 consumer quality devices.
- reflow all solder joints with 60/40 solder.
- clean PCBs and be aware of that glue goo used on caps as it becomes conductive over time.
- stortcircuit speaker A/B/A+B selector switches as these are often bad (and useless anyway).
- replace Q631, C631, D631, C632 and Q406. Measure R439 and replace if necessary.
- replace electrolytic caps as these are often worn out in 1981 consumer quality devices.
- reflow all solder joints with 60/40 solder.
- clean PCBs and be aware of that glue goo used on caps as it becomes conductive over time.
- stortcircuit speaker A/B/A+B selector switches as these are often bad (and useless anyway).
- replace Q631, C631, D631, C632 and Q406. Measure R439 and replace if necessary.
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Hi, I would replace all electrolytic caps but only after the repair has been done with success. For repair it seems handy to measure/replace C403 and C410 together with the other parts mentioned. Please take into account it may also be the 7317p (IC501) as it is pin6 that connects the relay via a transistor. It is a cheap but excellent IC and IME rarely fails. I would think of this IC after all the other parts would have made no difference. Intermittent issues are hard to solve. Freeze spray and a heater are then the tools but one can cause damage with that too. For the less experienced replacing the mentioned parts seems most effective.
Please use good parts as doing things right once is best practice. Panasonic FC still is good stuff.
So: Q631, Q406, D631, C631, C632, C403, C410 + reflowing of ALL solder joints in that circuits. Measure circuits and voltages at Q604 and Q603.
Please use good parts as doing things right once is best practice. Panasonic FC still is good stuff.
So: Q631, Q406, D631, C631, C632, C403, C410 + reflowing of ALL solder joints in that circuits. Measure circuits and voltages at Q604 and Q603.
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