Sony SL-HF950 Betamax - The wrong polarity! Part 1

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This one's a little bit different insofar as we're looking at a rather nice Sony SL-HF950 Betamax that came in for repair having had 12 volts applied the wrong way round to the CN power board.
A good service manual for this is here:
freeservicemanuals.info/en/se...
There are others out there but the scanning is so poor that you can't read the voltages or some of the component and connector numbers and I was battling with that before I found the above one.
Sorry for all the coughs in this one - I had quite a nasty cold! Sorry for all the 'ums'; I'm working on those!
Really sorry for the audio issues. Work in progress to sort those too and I'll fill you in on how I sort this!
Chapters:
00:00 Introduction
01:40 First checks
07:05 Connecting an external 12v power supply
11:14 Checking the standby circuit
20:13 Fuses on the SS-50 board and disassembly
26:19 Testing after N5 fuse replacement on SS-50 PCB
27:06 Standby issue and the clock chip
32:54 Coming out of standby and display issue
36:27 No sled/ skate movement
38:40 Display issue solved
39:40 No sled/ skate movement issue resolved
40:46 Testing and conclusion
#betamax #sony #mrbetabyte

Опубликовано:

31 июл 2024

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Комментарии : 12

@electronicwaves 4 месяца назад

What a coincidence. I also faced power supply issues with 2 VHS machines I bought recently and I made a video asking for advice. Of course, they are not vintage, valuable and rare like your Betamax unit!

@MrBetaByte 4 месяца назад

I'll have to check your video out. The HF950 is certainly quite a machine but saving any of these machines regardless of format keeps them from eventually fading away into history.

@KylesDigitalLab 4 месяца назад

I accidentally did this on an SLO-340 portable. Blew about a dozen diodes and probably some transistors on the main system control board. There's like 60 diodes just on the system control board and I had to check each one.

@MrBetaByte 4 месяца назад

Ouch! That's a lot of damage. In the end all that blew from the incorrect polarity on the HF950 was the three N5 semicondutor fuses - I found out today that the standby issue was the original fault with it before the accidental polarity swap.

@evidentsavant12 4 месяца назад

Hey there Mr. Betabyte. Been a while, but like a friend that shows up only when he has problems, you know where I am headed, I have a broken Aiwa AV-50M, that I got from EBay. Are you familiar with them? If so I need to find the spur gear that goes on the motor that drives the idler wheel. I have the service manual but the exploded views do not identify the part. Where can I find this info? From my measurements it is 6 mm in the outer diameter. There is a brass inset that it slides into on the shaft, so it does not slide onto the shaft itself. Well, I don’t know if it’s brass but metal of some kind and I have seen plastic spur gears that have that. Do I need to find one with the metal insert or willl it work just by obtaining a spur gear that fits around it? Thank you and keep on fixing.

@MrBetaByte 4 месяца назад

That sounds like a very interesting machine and I don't think I've ever seen an Aiwa Betamax. Is yours a PAL unit or NTSC? You'd probably get away with an all plastic gear but I'm assuming it has some twisting movement in use. Could you take some pictures of the gear and the surround mechanism and email them to me at mrbetabyte@gmail.com and I'll see if I can help locate one?

@VV-md2dm 4 месяца назад

Good day! I am your subscriber, I have been repairing SL-HF950 MK2 for 4 years.. Input 2 receives a square wave from IC301. And at input 3 there is a constant 3.4V. although there should also be a meander. As far as I understand, the summation of these meanders sets the voltage at the output of the op-amp to adjust the Dram speed. Question. Why does input 3 receive constant 3.4V when IC301 is working? What motivates her to do this? Please tell me what else can I see?

@MrBetaByte 4 месяца назад

What board are you referring too? What is the symptom/ fault with the machine? Is the 3.4v measured as AC or DC?

@VV-md2dm 4 месяца назад

@@MrBetaByteSS-50. On error amp pin 2 1.8 VDC, on pin 3 3.4 VDC(???). Symptom- slightly slower rotating drum... It is impossible to start recording - the machine goes to stop