Sony SL-HF950 expert needed
 

I am looking for an SL-HF950 expert. I recently installed a new power unit as described on Palsite (12v @ 4A) and now the machine powers on while it is cold. As it heats up, the machine appears to lose power and the reel motor gets weaker, the unit shuts down completely after a picture scan and it struggles to open the skate fully to eject the tape without a helping hand.

As I say, all these issues are non existent when the unit ia cold but it doesn't take long for these issues to materialise.

Does anyone have any advice of where I should be looking to troubleshoot these issues? I am guessing caps are faulty but no idea where.

Thank you

Re: Sony SL-HF950 expert needed
 

I suggest starting on the panel that supplies the power to the motors or go back on palsite and ask Noel Higgins his opinions

Re: Sony SL-HF950 expert needed
 

Is this any help? It's from palsite.com which I hadn't heard of until you mentioned it.
https://www.palsite.com/950tech.html
"replace the reel chassis" seems a bit drastic, but making a plastic spacer sounds doable.

Re: Sony SL-HF950 expert needed
 

Why did you fit a new power supply?
The most common failings on these are the two non polarised capacitors which go high esr and this wiped out one fusible resistor and two transistors.
I've seen this issue on quite a few.Other caps should be checked and changed if needed too but those ones are the usual suspects.

I've found if you replace those non polarized ones with GOOD quality ones maybe with a slightly higher voltage capacity and make sure that heat sync paste is refreshed then this seems to make these reliable.
Heat is the issue here after time and Noel resides in Australia so that will be more of an issue there.Hence the idea of fitting a different unit.

If your 950 has seen high miles the chances are some VU level meter led's will have expired.The hi-fi audio heads will have very limited tracking range and maybe the reel motor plastic bearing will have worn low so that the base magnetic area of the motor starts to lightly rub on the coils (NOT GOOD!).You will notice the normal Playback is affected on the Sony's and too an extent, the fast winds modes as it uses this and the search modes on the Sanyo and if bad enough will cause bad wow and flutter during play mode as it's in the capstan motor. IF this is the case.You will also hear a light cyclic scrape scrape sound as the base plate rubs on the coils
You can fit a tiny plastic bushing of a suitable material and it does work. I've had to do that on a few Sony's and a couple of Sanyo's too.Yes it works on those too but is fitted at the top bearing.

...Kevin

Re: Sony SL-HF950 expert needed
 

Thanks for everyone's reply

@Kevin,

The reason I fitted a new PSU is because that is what Palsite recommends. I tried replacing the non polarised caps already in the old PSU but a getting replacements for the fusible resistors and transistors are nigh on impossible unless you have a source? I concur with your findings though!

I don't know the history of this machine but the LED VU meters are all intact thankfully!

If you can kindly help me track down the components I would love to use the old PSU :)

Thanks!

Re: Sony SL-HF950 expert needed
 

I would try cricklewood electronics for the parts ,I assume you know the values of them

Re: Sony SL-HF950 expert needed
 

Thanks @dayrocket2

I tried Cricklewood Electronics. I need 0.5W and 0.47Ohms fusible resistor and they only have 0.25W and 0.47ohms or 1W and 0.47ohms

Can someone more knowledgeable than me confirm if I am able to change the rating of this fusible resistor in the primary part of the PSU without any consequences?

Also the transistors I need are 2SC3158 which has a power dissipation of 60W but their equivalents of 2SC3973a are 45W. Again please can someone more knowledgeable than me kindly confirm if I can change the values of these transistors without any consequences?

Many thanks

Re: Sony SL-HF950 expert needed
 

Hi
It's what Noel recommends and ,like i stated, he resides in a hotter country so any heat issues will be more prevalent.
I use CPC.co.uk or other reputable electronics providers. Yes it can be a slog but usually they turn up.Make sure too that heat sync paste is in good shape or refreshed as this will wipe those parts out in a short time if not.

...Kevin

Re: Sony SL-HF950 expert needed
 

Thanks Kevin,

Can you kindly tell me is this a wirewound resistor, metal film or a another type of resistor? Really struggling to find this from CPC, RS or Cricklewood electronics. I can get 1/4 watt or 1 watt at this value but I have no idea if I can change the rating without disastrous consequences

Re: Sony SL-HF950 expert needed
 

I reckon the 25 watt will be ok but its the correct transistors that may be critical it maybe worth asking Noel or Kevin if they are willing and can supply you these items or ask others on here for source of supply

Re: Sony SL-HF950 expert needed
 

Thanks @davyrocket2

Hi Kevin, can you help further please ? Do you have a supply of the fusible resistors and/or transistors as I am really struggling my end. I want to heed your advice and repair this PSU

Re: Sony SL-HF950 expert needed
 

Hi
Sorry for the late reply.
I will get back to you when i can.
Bear with me.


......................Kev

Re: Sony SL-HF950 expert needed
 

Oh and one other thing NEVER EVER Change the values of fusible resistors or indeed fuses as they are there for a reason.In the manuals these sort of critical things always have triangle symbols next to them.
It's for yours and the machine safety.

..Kev

Re: Sony SL-HF950 expert needed
 

Hi Kevin,

Many thanks for the update. I have been informed by a reputable electronics supplier that these are not fusibile resistors but are Cement WireWound resistors, is this correct?

Also in terms of the transistors, they don't appear to be mounted on any thermal paste or compound but a rubber membrane which then bolts onto the metal plate. I can pull the transistor away from this grey membrane with my finger, there is absolutely no paste anywhere to be seen.

However, inside the metal box there is a very thin layer of paste which seems to have dried out. This is where the back of the metal plate from the transistors bolt onto. I guess it is this paste you are referring to ? If so, could I renew this with thermal paste from CPU's?

Many thanks

Re: Sony SL-HF950 expert needed
 

As Kevin has correctly said do not change the value of the resistors ever .In regards the transistor equivilants then yes you can use them and get the cement wirewound resistors when you put it back together, then use some heatsink past in the area you mention. The rubber pad helps to spread evenly any heat from the metal of the transistor and the paste helps it to spread across the metal to assist cooling. I think the other part you should try to obtain is a pinch roller but it will not be easy to find however all of the Sony SL ,series will fit regards David

Re: Sony SL-HF950 expert needed
 

Hi all,

It seems I have been defeated by this fusible resistor. I simply cannot get hold of it for love nor money despite an extensive search. Hoping Sanbeta can step in and save the day, I hopefully have the transistors and capacitors in hand

Re: Sony SL-HF950 expert needed
 

Are these of any use to you? Bit pricey by the looks of things, although there is a 'Best Offer' option.

Re: Sony SL-HF950 expert needed
 

Willow 5

Sorry for the delay in getting back to you.

I've just pulled the info from the 950 service manual.
R611 is the fusible resistor.It does'nt state if it's cement type but it is an unusual looking substance. value is 0.47ohms 1/2 watt.
Sony part number is: 1-217-418-21

The two transistors are made by NEC 2SC3158 and are in positions Q601 and Q602.

The heat thermal paste goes in between the two metal casing areas, and as you pointed out yours is dried up. Heat is the killer here.The transistors have a rubber type membrane .
There are also two non polarized caps that have always gone high ESR when these fail too.I would go with a good quality make and a slightly higher volt rating.to give extra protection.
I can't remember the values but no doubt you will have your psu to see these.

Hope this helps?

Let us know how it goes....................Kev

Re: Sony SL-HF950 expert needed
 

They are indeed the correct ones and PRICEY too.A shame many do that when things are hard to get!

Re: Sony SL-HF950 expert needed
 

Wow thanks all! Great news that the part is now available on ebay, must have only just come online as last time I looked it was not there. Thanks all so much for all your help and advice. Is there an IC that also needs replacing some sort of regulator?