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Old 14th Oct 2020, 6:59 pm   #21
willow5
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Default Re: Sony SL-HF950 expert needed

The Bipolar caps are 47uf 25v capacitors. Can I stick with these values or increase the voltage? I have ordered like for like for now, will it cause any problems?
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Old 15th Oct 2020, 9:19 am   #22
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Default Re: Sony SL-HF950 expert needed

Hi.
Sticking with the original spec is the correct way as this is what the circuit designers have used and these circuits are given rigorous testing, there is no harm at all to use a higher voltage component but going considerably higher in voltage can in some cases cause issues, 30-50v though is fine in this application so long as they fit physically.
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Old 15th Oct 2020, 1:38 pm   #23
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Default Re: Sony SL-HF950 expert needed

That's great advice! Thanks very much 👍
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Old 15th Oct 2020, 2:57 pm   #24
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Default Re: Sony SL-HF950 expert needed

I have bitten the bullet and bought that very expensive resistor but I had no choice as it is so hard to find! Probably the most I have ever spent on a resistor! Will let you all know how I get on with this repair. Thank you for all your help and advice
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Old 17th Oct 2020, 1:11 am   #25
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Default Re: Sony SL-HF950 expert needed

I probably should've said you can go to a higher voltage or the next one up from original.You must always stay the same for the uf rating though.

Please do keep us posted.

....Kev
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Old 17th Oct 2020, 10:53 am   #26
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Default Re: Sony SL-HF950 expert needed

Quote:
Originally Posted by willow5 View Post
I have bitten the bullet and bought that very expensive resistor but I had no choice as it is so hard to find! Probably the most I have ever spent on a resistor! Will let you all know how I get on with this repair. Thank you for all your help and advice
I think I would be too scarred to put that resistor in until I was sure I had fixed all the faults

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Old 17th Oct 2020, 11:35 am   #27
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Default Re: Sony SL-HF950 expert needed

Thanks all. I am really scared to even touch the thing!

The bipolar capacitors are currently 47uF and 10v (and have a high ESR of between 1.2 and 1.3) so would it be ok if I go to a 47uf and 25v?
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Old 17th Oct 2020, 10:48 pm   #28
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Default Re: Sony SL-HF950 expert needed

As Kevin has said do not change the uF rating you can go up slightly on the volts. What you can do is ask for capacitors with a higher temperature rating most are 85C what you can request is for some 105C which will withstand more heat, which I am sure Noel does being in a hot country.

Do make sure to replace those transistors, apply heat sink compound and make sure the solder area is clean, but yes a sight increase in voltage is OK provided there is enough room.
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Old 18th Oct 2020, 2:42 pm   #29
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Default Re: Sony SL-HF950 expert needed

Thanks @davyrocket2. I already replaced the transistors, haven't yet applied the heat sink compound as theybare mounted durectly onto the rubber membrane. This will be the last step for me before I screw everything back together. I cleaned as much as I could from the glue near the solder pads for the transistors but a lot still remains. Will this cause a problem longer term? Are they electrically sensitive components when soldering or can I handle them with my fingers?

I have noted your comments on the capacitors. Ordered the 25v already but will see if I can get something nearer the 10v rating.
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Old 18th Oct 2020, 9:18 pm   #30
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Default Re: Sony SL-HF950 expert needed

if it was me I would clean the holes insert them as ready end just gently solder ensuring it flows well after inserting the membrane and heat sink compound
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Old 22nd Oct 2020, 8:20 pm   #31
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Default Re: Sony SL-HF950 expert needed

I know this looks a bit of a mess but would this pass as an ok job for the transistors?
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Old 22nd Oct 2020, 8:53 pm   #32
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Default Re: Sony SL-HF950 expert needed

A solvent such as IPA, and a fairly stiff brush will clean that up. Cosmetic though, it won't work any better!
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Old 25th Oct 2020, 2:57 pm   #33
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Default Re: Sony SL-HF950 expert needed

All working thank you all so much!!!!
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Old 25th Oct 2020, 5:48 pm   #34
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Default Re: Sony SL-HF950 expert needed

Small glass fibre brush if you can get one.
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Old 25th Oct 2020, 9:29 pm   #35
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Default Re: Sony SL-HF950 expert needed

Only slight issue with rew picture scan where I am getting these awful noise bars. Any further advice appreciated.

Fwd, still and play all work fine
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Old 27th Oct 2020, 11:34 am   #36
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Default Re: Sony SL-HF950 expert needed

Congrats Willow on getting this classic working again.
Your comments on that board area that's a bit scruffy.i always use an old toothbrush and rub lightly with IPA and it cleans all that off nicely.
Some who like to go the extra mile like to replace that protective coating as it get's damaged by the heat.

As for those thick noise bars during reverse search.Could either be the back tension,partly worn heads or heads that need a clean.
I would avoid cleaning them manually though unless you really know what you are doing.
I've had two of these models sent to me where a couple of the head chips have been broken in half or completely off,no doubt by the over zealous cleaning.These not only have three visual heads for clean trick functions but the two other ones for the Beta hi-Fi and are expensive IF you can find any.

If it's just a slight clog then playing a really good quality tape will clean them 99% of the time. Without the risk of damage.
Also i would recommend switching this off from the power when not in use for long periods of time and also switching OFF the VU level LED's as they are notorious for failing led's after time.Just use them for critical Hi-Fi recordings.
Also keep all modern gear away from these too.Some models readily pick up signals from Wi-Fi often blamed on the vcr itself.
Keep items off of this too as some like to cram as many bit's of gear into one stack as they can and keep those heat vents clear too

Regards...................Kev
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Old 28th Oct 2020, 12:05 pm   #37
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Default Re: Sony SL-HF950 expert needed

Hi Kev

Many thanks for your message of support! I didn't do any more on that circuit board as I already put the thermal paste and left well alone!

Now the issue with the picture scan is that when in rew, the tape appears to leave the drum for some reason. Also general rewind is slow as the supply reel gets heavier with tape especially near the start of the tape.

I think these 2 issues are possibly linked but upon closer inspection, the top drum is totally shiny which could mean the tape is sticking to the drum? I tried rubbing the top drum down but now getting a line across the screen in play mode. I took extra care not to touch any heads during this cleaning process
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Old 28th Oct 2020, 12:11 pm   #38
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Default Re: Sony SL-HF950 expert needed

Shiny is just normal or wear and tear,tapes do not stick without major problems.
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Old 28th Oct 2020, 12:34 pm   #39
willow5
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Default Re: Sony SL-HF950 expert needed

I saw a video here where scuffing the surface actually decreased the friction.

https://youtu.be/sxRVnr2mSsg
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Old 28th Oct 2020, 1:52 pm   #40
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Default Re: Sony SL-HF950 expert needed

The only thing is with the lower drum assembly and they do drag and if lucky can be cleaned with Dura Glit.
Never had to polish upper drum,only marks have been caused by too much back tension which wears the head tips very quickly.
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