Sister Sony on the bench (STR 6060)

[nj pheonix]

With the help of the forum i snatched victory out of the jaws of defeat on my 6065 which i'm listening to now. I'll have to revisit for lamps but otherwise its done. So , as i alluded to (to crickets) in the last thread, I'm aping Leestereos 6060 update / improvement on a STR 6060.
Things so far are going smoothly. I opted to replace the carbon comp resistors on the amp boards (except for 3) to get at them would require substantial disassembly which i can't justify. They do check in spec.
Just for the record, i'd say about half weren't in spec.
So, before i start reassembling these, I noticed one channel has the original 2SD88 outputs. The other has RCA 3438 outputs (SK is written in another place) so obviously they've been replaced. Here's the question
It was working fine before i started. Should i just leave them be?
Here are alternatives on hand.
I have another pair of 2SD88s (they came for the other, the lesser matched pair).
I have a pair of TX 183s
I also have a new quad of MJ5003Gs
Or is there a better way to go?
I was sort of leaning (barring a more seasoned voice chiming in) clean, new thermal compound and leave.
What do you think?

 

[Moving Ahead]

I suppose it all depends on if you want the job done right.
I know why people do this and it works.
Maybe if you can answer- if its a keeper or not? will help define your course of action.
In my minds eye the mismatched whatever will always taint my experience.

 

[nj pheonix]

Best answer to that question is I don't really know.
From that perspective, I'd go on as if it were a keeper.
I'm not paying for bench time, No one is waiting for it, clearly not a business to me (I think my tech work is some kind of personal therapy) , so really it's just a few relatively inexpensive parts.
So?
Oh., on that note it brought up another question .
I tend to work on tube gear. Most PP tube amps benefited from matched outputs.
I've seen SS designs where they made a point of matching output transistors and other designs where even the manufacturer didn't bother.
I was wondering whether Sony did in these and if I were to buy new outputs whether I'd be better served to buy say 10 and try to match up 2 pair as best I could.
Or, is that a waste of time and money?

 

[Moving Ahead]

so really it's just a few relatively inexpensive parts.

TO-3 outputs are generally $5-10 pop. Replacing all 4 can add up. Thats usually why people only replace the defective item, but IMO thats not right.

Most PP tube amps benefited from matched outputs

Well yes if you're wanting it to be right. However the outputs have the least impact on the sound. Thats done in the early gain stages.

they made a point of matching output transistors

Yes Sony surely did this on the 6060. With this vintage you often see a code printed on the case or even a color coded painted dot , indicating the Beta.
There could be reference to this in the service manual- when replacing outputs. Also part numbers might indicate something.

buy say 10 and try to match up 2 pair as best I could

Waste of money.

If it was me I'd look to see if the new 2SD88 match the old 2SD88. visual, hFE, weight. Did you purchase from reputable source? If I can convince myself they are what they are I'd use them.
If for some reason they don't stack up I'd go for the modern substitute with no hesitation.

I'd take a look at the outputs to see if they are welded in. If they are- don't apply too much heat on removal and installation, also the connecting leads might be short so keep that in mind.

 

[nj pheonix]

I am confident they're authentic.
The pair I used in the 6065 (of 4 I bought ) were the best matched pair.
I will say the the newer production outputs I've bought seem to be more consistent piece to piece.
I see in the 4-6 dollar range. If you don't figure in shipping , that's not so harsh for a hobbyist. Like I said, I don't plan on making a profit.
I think I also have 6 pulls of original outputs from an mc2100 which were good. I might be able to match up 2 pair.
( they are a similar output, I'm not randomly sticking in anything)
They are soldered. Thanks for the tips

 

[leesonic]

I would say do whatever you have to do to get the output transistors the same on both channels, new or used. I have restored enough of the NAD 3020 amplifiers to build up a collection of original RCA and Motorola 2N3055/MJ2955 outputs. I've also managed to do this with Kenwood KA-7100 and Pioneer SX-626 output transistors.

It's also good that you're pulling the output transistors and applying new heat transfer compound, or heat sink grease, whatever you want to call it. I see "restorations" done all the time, and the original outputs are sitting there, dry as a bone.

Oh, and...





Lee.

 

[nj pheonix]

To accomodate my friend Mr Sonic

The 3 resistors i was talking about are blocked by stuff on backside i'd prefer not to dismantle.
You can see the Sony and RCA transistors (i prefer sockets). Otherwise no surprises so far. Oh and the different color pot. I'm thinking it wasn't factory

 

[Moving Ahead]

The daughter-board on the output stand-off (thermal tracking diodes) needs to be greased & seated properly. Are the RCA the same height as the older Sony outputs?
I wouldn't trust those trimmer pots (bias & cen volt.) at this age. Sealed Multi turns are the go.
Whats the bias setting on this unit?
Looks like plenty of resistor changes too. Any reason?

 

[nj pheonix]

i really changed the carbon comps because they're inherently inferior in general.
I have been testing them as i pull. I'd guess (i haven't been keeping count) a third to half were out of spec.
I didn't check bias before i started. I figured i had to rebias at the end anyway so it was somewhat pointless.
The RCAs were definitely somewhat shorter.
I'm open to suggestions for new pots.

 

[petehall347]

matching outputs depends on the design .. if in parallel they should closely match so they all work together .. or you hope they will ..

 

[nj pheonix]

'm open to suggestions for new pots.

You don't all have to jump in at once
They are 10k and 50k

 

[leesonic]

Get some Bournes ones, multi-turn are nice, but they don't have to be. You might have to make some adaptor boards to mount them. Have look at my Pioneer SX-626 threads, just search for SX-626 in the title, and posted by leesonic. I will try and get you some part numbers when I get home.

Lee.

 

[leesonic]

Multi-turn

652-3296P-1-103LF
652-3296P-1-503LF

Single turn (make adapter boards like my picture below)

652-3309P-1-103
652-3309P-1-503

 

[nj pheonix]

Thanks Lee,
I saw those at your house.
I placed an order tues .
I should be good.
Either what i ordered will fit or I'll make adapters as shown if necessary

 

[EngineerNate]

@leesonic Where's your favorite place to buy perfboard? I'd like to get some in stock for small PtP projects and things like this.

 

[Moving Ahead]

You're probably a fair way through the job. Remember to test at intervals and with a DBT.

I only pass by here on the weekend and being down under it generally takes a while to log on. With the trimmer question , I'd entertain the thought of removing the original with solder pump, take measurements, remove locking washer, disassemble and break off the resistance track under. At this point you have a vintage daughter board to mount the new trimmer adjusted to measured resistance.
I've also had success with this type but adjusting can sometimes be hindered by pcb real estate.


The multi turns are one of those simple pleasures I don't mind recommending.

matching outputs depends on the design .. if in parallel they should closely match so they all work together .. or you hope they will ..

I guess we are in agreement.

 

[nj pheonix]

I like the trimmer idea.
I'll have to try that.
I had bread board for the task.
Been working a lot of overtime.
Heading into N.Y. now.
So project is going verrrrry slowww

 

[leesonic]

@leesonic Where's your favorite place to buy perfboard? I'd like to get some in stock for small PtP projects and things like this.

Mouser part # 854-ST3U

Lee.

 

[Moving Ahead]

I'll have to try that.

I forgot to say,- tin the vintage leads first. , it makes the job much easier.

 

[nj pheonix]

OK so some success and some failure.
I finished recapping, I was able to daughter board the old controls with multi turn pots. i opted to go with the onsemi mj15003gs (so that i had 4 matching) I put on a dim bulb and it passed. While on dbt i wanted to see where bias was showing (i measured old pots when i removed and set new to same value before i installed) . I was going to purposely dial them low on the dbt and then slowly dial them back up after i applied full voltage. First channel looked normal. I have almost no ability what so ever to turn up the other channel so i screwed something up. I'm calling it a night today, but hoping for suggestions.