Sansui 9090DB Restore Part 5 Dolby Board

[@TrevorsBench]

Good to hear you're feeling better Ray

[@raygianelli3612]

Thanks Trevor. That makes two of us!

[@TB-nz4kf]

Good to hear your on the mend.

[@raygianelli3612]

Thanks TB!

[@josephlalock8378]

those short leads on the film caps are called "pc pin" as the termination style SOMETIMES. but they don't always make note of it. choosing the lead style, length, distance apart are as much work as any other part of capacitor choice. one must really have to have a passion for doing this as they don't make any part of it easy on us. glad you're doing better bro.

[@raygianelli3612]

Word. I've ordered a LOT of stuff that wasn't what I thought I ordered when it arrived. Appreciate yui wishing me well, Joseph! This getting older thing doesn't seem to have a lot of upside. 😦

[@mornax]

Nice video. Probably too late for you, but I recently finished reverse engineering the Dolby board for a friend that asked me to help. It's an exact copy of the layout with some improvements, such as putting the four backside resistors on the front, completely documenting the switch, and a cleaner schematic. Found some interesting Sansui errors along the way.

[@raygianelli3612]

Nice! A lot of manufacturers made errors in their schematics, and few ever released revisions.

[@bill_p2074]

Glad you’re back. Be careful at work - you’re not a spring chicken any more!

[@raygianelli3612]

I'm starting to get a sense of that, Bill! It's just taking a long time for this cleanup project because my CO is 11 stories and it's been a dumping ground for decades.

[@officialmikethompson]

Good tip on the re-pinning; I hadn’t read that yet and that could very well be what I’m seeing wrong on the 9090db on my bench currently.

[@raygianelli3612]

Mike, this is a known issue with these. The procedure is quite tedious, as there are 64 through holes that need to be pinned!

[@officialmikethompson]

@@raygianelli3612 certainly having the Hakko tools to do the job makes it a hell of a lot easier. The FR-300 was money well, well spent. I got that board re-pinned in a couple hours.

[@raygianelli3612]

@@officialmikethompson +1 They're a great tool, and while not cheap worth every penny.

[@roroseppel2077]

Nice job on a very consuming time project !

[@raygianelli3612]

Thanks! I must confess that I really prefer repair work to restoration.

[@andymouse]

Glad your feeling better, and God Bless America for giving us the Cheeseburger !....cheers. Oh yeah I have the same green laser ! Awesome !

[@raygianelli3612]

Thanks Andy. That laser is terrifying. At least the cats think so. 😁

[@simpleperson3234]

Hello, Sir. I have a question regarding 9090DB, which I am trying to repair. Two channels work in Mono, but in Stereo, the right channel is dead, and the left is still working. I did change the capacitors on Dolby Board and improved the connections in feed-throughs; Replaced the ribbon cables on the Dolby Board; Sprayed all switches with Deoxit multiple times; replaced all resistors and all capacitors on Driver's Board. Recently I did an experiment, I placed the Driver's Board reversely to the power supply board, and the channels got reversed. The left channel was dead, and the right was working. I assumed that Driver's Board or Power Supply board was the problem. I decided to measure the output voltage pins on the power supply board with a multimeter, where I connected the driver's panel and noticed that the far left pin gives 3mV volts and the far right pin is 60 V., but the rest of the pins are equal to each other. What is the problem in your opinion, Sir? I am very thankful you are posting such valuable videos about the repair. I enjoyed watching them and hope to hear back from you soon.

[@raygianelli3612]

Are you getting good/equal signals from the preamp out jacks?

[@simpleperson3234]

@@raygianelli3612 Yes. The signals are equal.

[@raygianelli3612]

@@simpleperson3234 Make sure the right channel fuses are good, and by good I mean that they've been checked with an ohmmeter. If good make sure that you have both positive and negative voltages at the right channel output stage.

[@Anth4044]

Can someone please answer this question please can I hook up my reel to reel without having to do anything with the dolby board? It may be a dumb question I just dont want to affect anything with that board. I just want to play reel to reel and record only if it doesn't have anything to do with the dolby. I know the boards have alot of trouble thanks if anyone could help me.

[@raygianelli3612]

If it's currently working then there's no reason why you can't hook it up. The Dolby board issues usually result in one channel failing.

[@Anth4044]

@raygianelli3612 Gotcha thank you so much for helping me with my question. I hope you have a Happy New Year👍👍