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P-Sussex · 15th Jan 2021, 8:44 am

Sony SL-C7 Rebuild Alive for 20 Seconds Then ‘POP” & Smoke.

I have been rebuilding a Sony SL-C7 and I fear I may have taken on more than I can chew, with my experience.

The machine initially was Red light only with dead clock, no Green light when switched on. No other life. I began in the PSU replacing C110 & C101 (4.7 350v), heat sink transistors Q101, Q102 [2SC23351, surge resistor R101, ICI TL494CN (with heat sink protection when install). The main suspect diodes were removed from the board and tested as OK and simply replaced. I also replaced many of the other E. Capacitors for good measure as I had them to hand.

I then worked on the Timer boards, removing the very badly corroded battery. I had to remove the ribbon cables on the battery board and give it a good clean. On reattaching the cables I checked the paths of the connectivity from the ribbon cable wires. Many just seem to pass through to the other side of the board, and pass directly where the battery was. So many of these lines on the PCB were gone due to corrosion. Anyway I decided to bridge these wires from one end of the board to the other, crude but at least I had connectivity between the three boards.

The dead push switches where replaced on the timer board and tested for continuity for each one. So far so good.

So when it cam to testing: In Stand By mode Red light on, I was surprised to see the clock worked, I could even press the Clock push switch and the clock started its count from 00:00, so clock OK.

Next came the On switch. Green light came one and there was life. At this stage I was feeling really pleased with myself. I decided to put a tape in and pressed the eject, yes eject worked, marvellous. Then the sound of a crack, pop from the PSU area, Then some smoke. So the green light was on for about 20 seconds. It was hard to tell where the smoke came from but coming from the area where the timer meets PSU. The glass fuse F006 has gone, seriously blacked out. (Do fuses like this cause smoke?)

I changed the fuse and tried again, yes I didn’t appreciate at the time I could cause more damage, but totally dead now not even life to the timer/clock from the ‘Ever Power Supply’. No Red light.

I realise the dangers of working on switching PSUs and don’t want to poke around unsafely with it switched on, unless I fully understand the areas I am checking.

I do have a second C7 machine also purchased in a similar state, my thinking was to make a good machine out of two. So I have access to second set of parts.

So my question is will the replacement/checking of the initial parts that I replaced be futile? What parts should I be looking at? The crack/pop sound is this sound typical of a particular part that blows which I can easily check.

I notice from my PSU checking that one of the Q101/102 2335 transistors has gone so far. The replacement diodes appear OK. Have not checked the E. Capacitors yet.

I am also in the process of double checking all my work on the timer/clock boards in case I have created a short somewhere which caused this.

Any thoughts and pointers would be most welcome.

My experience is beginer level.

Thanks in advance.

15th Jan 2021, 8:44 am	#1
P-Sussex Triode Join Date: Dec 2020 Location: Horsham, West Sussex, UK. Posts: 17	Sony SL-C7 Rebuild: Alive for 20 Seconds Then ‘POP” & Smoke Sony SL-C7 Rebuild Alive for 20 Seconds Then ‘POP” & Smoke. I have been rebuilding a Sony SL-C7 and I fear I may have taken on more than I can chew, with my experience. The machine initially was Red light only with dead clock, no Green light when switched on. No other life. I began in the PSU replacing C110 & C101 (4.7 350v), heat sink transistors Q101, Q102 [2SC23351, surge resistor R101, ICI TL494CN (with heat sink protection when install). The main suspect diodes were removed from the board and tested as OK and simply replaced. I also replaced many of the other E. Capacitors for good measure as I had them to hand. I then worked on the Timer boards, removing the very badly corroded battery. I had to remove the ribbon cables on the battery board and give it a good clean. On reattaching the cables I checked the paths of the connectivity from the ribbon cable wires. Many just seem to pass through to the other side of the board, and pass directly where the battery was. So many of these lines on the PCB were gone due to corrosion. Anyway I decided to bridge these wires from one end of the board to the other, crude but at least I had connectivity between the three boards. The dead push switches where replaced on the timer board and tested for continuity for each one. So far so good. So when it cam to testing: In Stand By mode Red light on, I was surprised to see the clock worked, I could even press the Clock push switch and the clock started its count from 00:00, so clock OK. Next came the On switch. Green light came one and there was life. At this stage I was feeling really pleased with myself. I decided to put a tape in and pressed the eject, yes eject worked, marvellous. Then the sound of a crack, pop from the PSU area, Then some smoke. So the green light was on for about 20 seconds. It was hard to tell where the smoke came from but coming from the area where the timer meets PSU. The glass fuse F006 has gone, seriously blacked out. (Do fuses like this cause smoke?) I changed the fuse and tried again, yes I didn’t appreciate at the time I could cause more damage, but totally dead now not even life to the timer/clock from the ‘Ever Power Supply’. No Red light. I realise the dangers of working on switching PSUs and don’t want to poke around unsafely with it switched on, unless I fully understand the areas I am checking. I do have a second C7 machine also purchased in a similar state, my thinking was to make a good machine out of two. So I have access to second set of parts. So my question is will the replacement/checking of the initial parts that I replaced be futile? What parts should I be looking at? The crack/pop sound is this sound typical of a particular part that blows which I can easily check. I notice from my PSU checking that one of the Q101/102 2335 transistors has gone so far. The replacement diodes appear OK. Have not checked the E. Capacitors yet. I am also in the process of double checking all my work on the timer/clock boards in case I have created a short somewhere which caused this. Any thoughts and pointers would be most welcome. My experience is beginer level. Thanks in advance.