Resurrecting 70's audio components

[Stuey]

Hi there,

I recently picked up a load of nice Onkyo gear which I would like to bring back to life. I have a CP700-M direct drive turntable, A-5 integrated, T-9 tuner and a TA-630D cassette deck, along with S-8000 speakers. It all came in the proper cabinet and although terribly soiled, under the dust it is near mint. Oh, and it was a non-smoking household.

All the units work, but as far as I'm aware the elderly owner didn't use the equipment much over the last while.

Please...can I obtain some advice from you knowledgeable people about which internal components I should just replace forthwith? Capacitors in the PSU's of the components....etc.

I don't have a variac and am quite good at desoldering and replacement of components without damage.

Please don't think I'm rude if I don't reply to any posts for a couple of days as I'm going into hospital tomorrow for an op.

Cheers

Stuey

 

[Conrad Hoffman]

I've always thought replacing components without confirming what was wrong with them is foolish. Without a scope, it's just reckless. It causes "technician blight" which is an often terminal disease contracted by perfectly good vintage equipment. Filter caps, the usual target for replacement, are completely unpredictable- some go in a year, some are near perfect after 40. First, clean everything up, both inside and out. Be sure to do a very careful visual inspection of every component and connection, using a magnifier if necessary. Then do a careful listening evaluation to see where you stand. Keep in mind that some Onkyo stuff is excellent, but they also made a lot of mid grade stuff that was good for the money, but not top shelf (like my T-10 tuner that's pretty but ordinary). Then make a plan, dividing it up into "seems to need work to return to factory specs", and "has great potential with a few mods". Maybe a third category, "eBay". Then decide what to tackle first and see what people here can offer.

 

[Stuey]

Thanks Conrad. I did wonder if leaving things as is, unless there was an obvious problem, was the best way to go. My main concern was about whether a component might cause significant damage to other parts NLA, such as transistors (of course most can be replaced with equivalents, I know).

The main components I was interested in was the tuner and cassette deck, although I kinda did like the thought of having an almost mint retro 70's system in the house. Until I heard the speakers...they are quite poor sounding when connected to my known good equipment. I've read that the T-9 can be quite reasonable, and the cassette deck. I don't have much choice at the moment as I don't have a deck any more, but have about 100 cassettes.

Thanks for the heads-up on the value of Onkyo gear, too. However, at this stage I don't have anything I'd call high-end anyway! Ha Ha. Just mid range Marantz, Rega and DIY. But getting there slowly.

I will take your advice. Thanks.

Any more tips greatly appreciated.

Stuey

 

[lineup]

Any more tips greatly appreciated.

Stuey

Old Integrated amplifiers and Preamplifiers.

Besided Power supply caps, there are a few things that can become 'worn out'.
These are any mechnical moving parts.
Like carbon potentiometers and frontside switches.
Switches that are used for controlling the audio signal.
Even electrical relay switches/contacts have not unlimited lifetime.

The Potentiometer most use is The Volume.
Such a pot of carbon type may have a lifetime of some thousand turns.
After this the resistive carbon layer can be very damaged.
We can sometimes hear 'scratching, rasping sound' from such old potentiometers.
While turning volume up and down.

Lineup

 

[Stuey]

Thanks Lineup!

Interestingly, the volume pot on this one doesn't crackle, but is VERY stiff. I guess the grease has gone hard with age. I usually use a tiny amount of lighter fluid followed by contact cleaner spray - but I haven't done this yet.

Cheers

Stuey

 

[Mayank]

Stuey:

Start with one equipment at a time.

1. Follow Conrad's advice. Before doing anything, perform a DETAILED visual inspection. Take notes. Look for any oil/grime stains/leaks. Then clean it inside/out with a small brush and q-tips where necessary. Check for any burn/dark patches or smell on the PCB. These are all clues.

2. Do NOT use WD40 or the common 3-in-1 oil (it is vegetable oil based). Deoxit is OK for the pots which could be scratchy due to age.

3. Just because you are comfortable with desoldering/soldering, resist the urge to replace components at random.

4. "If it ain't broke - don't fix it". A modest multimeter can be really useful. Voltage checks can be done if you have access to the schematic or the service manual.

5. Vintage Cassette Decks and turntables will typically need new belts. I usually get these cheap here at MATelectronics, but I am sure you will find similar mail order stores in Australia.

6. Speakers could need surrounds replaced if they are foam.

7. The A-5 integrated amp is a basic 50WPC. Fairly rugged. PM me if you need the Service Manual.

Good luck and wishing you a speedy recovery.

Mayank

 

[Stuey]

Cheers Mayank. I also work on ~70's cameras so I know the 'danger' of WD40! Thanks for the tips.

I already have the service manual for the A-5. Depending on the sound, I may even mod the pre section - I believe the preamp can benefit from an op amp replacement - something like the OPA 2134 which I have a few of. First things first, though...

Cheers

Stuey

 

[Conrad Hoffman]

Ah, '70s cameras, one of my other loves. Everything you know about servicing gummy gunky shutters and such, applies to pots and tuner mechanisms. The Ronsonal lighter fluid should free the sticky pot shaft- as you well know, some of the old greases somehow magically turn themselves into epoxy over the years. Try to find some Nye damping grease like Nyogel 779 or similar. This will give a nice silky feel to the controls if you can work it in there. I highly recommend Caig DeOxit and their other products, over garden variety contact cleaners. Radio Daze sells that and a lot of other useful vintage repair stuff. IMO, op-amps were the weak link in vintage equipment, where they were foolish enough to use them. Today's parts are vastly better and probably a good place to start with mods. Though I haven't built one yet, there's an on-line "ESR checker". It's an ohm meter using a high frequency AC signal. This is probably the easiest way to check for bad filter and coupling caps without removing them from the circuit.

 

[DreadPirate]

I have about 50 pieces of '70s vintage equipment, just can't pass on them when I come across them. I'm a beginner tinkerer, but do have some tips. Deoxit or Faderlube to clean the controls, NOTHING ELSE. Always hookup junk speakers to an amp of unknown condition. Press and depress all buttons several times, one that has not been operated for decades could blow speakers on activation. Check DC offset and bias. Visually inspect for leaky and bulging top capacitors, keeping in mind that many were glued down with brown goo which could resemble a leak. Its a good idea on some equipment to have the speakers offline on turn-on and disconnected prior to turn off (using the speaker selector switch), the user manuals usually state this. Careful cleaning face plates and glass, the lettering on some comes right off.

If the unit is working fine, no sense in replacing ANYTHING. You will most likely degrade, not improve sound. Most units I have initially may have had minor issues like needing cleaning, lamps, etc or were dumped because of a specific fault that needed fixing. Otherwise, they have worked fine. Things were made better then.

I have at least a dozen '70s era speakers and believe there isn't much worthwile there, but that is just my opinion.

Love that old stuff...

 

[Stuey]

Ah, '70s cameras, one of my other loves. Everything you know about servicing gummy gunky shutters and such, applies to pots and tuner mechanisms. The Ronsonal lighter fluid should free the sticky pot shaft- as you well know, some of the old greases somehow magically turn themselves into epoxy over the years.

I used to have quite a few cameras, but only retained a couple of lovely Pentax Spotmatic bodies and a reasonable spread of matching Takumar lenses. My favourite cameras; I guess they're the camera equivalent of the 70's Japanese audio gear, build quality wise. I do my own repairs and know the value of Ronsonol!

I'll get some DeOxit - it's sold here and I've read enough recommendations now... For damping grease I have some I use for camera lenses which is used by the Aussie military in binoculars.

Thanks for the replies, guys. Keep them coming...!?

Cheers

Stuey

 

[Nordic]

When I resurrected that old 70's Sansui earlier this year, the greatest improvement in sound was simply returing it to factory specified bias and offset levels.

 

[jackinnj]

First, clean everything up, both inside and out. Be sure to do a very careful visual inspection of every component and connection, using a magnifier if necessary.

I have been amazed at how cleaning up a piece of equipment will make it feel better -- whether it's a old Hallicrafters receiver or a piece of Krohn-Hite test equipment.

 

[Stuey]

I think you're right, Jack!

I've almost finished cleaning up these components. They are absolutely mint. None of them is marked in any way whatsoever, anywhere, because they've spent their whole lives in the one house and in the original glass fronted cabinet. I'm happy...

In addition, everything works, including all of the displays and bulbs.

Luckily the two massive 'Coke can' 13,000uF Integra branded capacitors in the A5 seem fine. Gee, Onkyo used a fair size of transformer in this thing! It's huge, for the modest power of the amp!

The only issue is that the belts on the cassette player have turned to tar. I'm looking for a service manual which I don't strictly need to do the job, but it might help in dismantling the mech and would be nice to have as I have the others.

Cheers

Stuey

 

[jackinnj]

The Onyko repair manual is available as a Sam's Photofact -- just put 630D or TA630D into the search engine -- the Sam's website allows you to download.
http://www.samswebsite.com/description.asp?ID=Photofact
Sometimes the manuals show up on EBay for $5 to $7.

 

[lineup]

When I resurrected that old 70's Sansui earlier this year,
the greatest improvement in sound was simply returing it to factory specified bias and offset levels.

Good point, Nordic

The amplifier will work as intended, from the design idea first beginning.

 

[Stuey]

Thanks Jack, I got a manual from ManualsParadise for $19 before I saw your post. Quite good service; the download was available in about an hour.

The Onkyo manual was almost useless for changing the belts though. I had to basically work it out myself. However, I got the job done and it's working really well. Not a bad deck either.

Cheers

Stuey

 

[unclejed613]

yes, a lot of really nice cassette decks have only 1 thing wrong with them..... the belts have turned into goo. you may want to use rubber renew on the pinch rollers if they're in decent shape. the surface layer of rubber gets dried out and hard. keep the rubber renew away from plastic parts. some rubber renew compounds have solvents that will eat plastic. you want to check the heads for wear. if you can master it, the skill of lapping the heads can save you a lot of money and time. practice on junk heads until you get it right. after you get the deck working, record a 3khz tone on a known good tape deck. then play it on the one you repaired. while playing it, feed audio from the deck to a frequency counter. set the motor speed pot for 3 khz. the count may vary a bit, that's wow and flutter. you might be able to find a wow and flutter meter on ebay. the best ones had a crystal controlled PLL. for making a test tape, the oscillator put out a rock solid 3khz. when playing back and testing wow and flutter, the output of the PLL phase detector drove a meter movement. you will also need a 15khz azimuth test tape. you can also make one of these if you have a known good tape deck. while adjusting the azimuth, you are looking for maximum output at 15khz. i've also used commercially recorded tapes and done azimuth by ear (listen to the high end, especially the cymbals). it's rare to find a commercially produced tape with the wrong azimuth. they had to keep the customers happy.

 

[jackinnj]

wrt belts -- you just might want to try McMaster Carr -- they have zillions of belts in stock and service is virtually next day.

 

[Stuey]

Thanks guys. Gee, this forum is good.

I bought a bulk belt pack from our equivalent of your Radio Shack (called Dick Smith over here) for $8 and it had belts which fitted satisfactorily, although the wide flywheel belt needed careful trimming with very sharp scissors to narrow it from 7mm to 5mm.

I've kept 'McMaster Carr' in my notes though.

Thanks for those tips Jed. That might be a job for when I've done most of the other refurbishment and possible mods to the units. I polished the heads with isopropyl and a Q-tip (cotton bud) and the play head came up really shiny and unworn.

I've never heard of Rubber Renew - where does one get it? I did note that some of the rubber idler wheels were slighly dried.

I must say that this deck is possibly the best I've heard (while admitting I haven't critically listened to, say, a Nakamichi although I once heard one at a party...).

Thanks again...

Stu

 

[Stuey]

Oh, I spoke too soon. The tuner doesn't provide a stereo output. At first I just assumed it was the basic test antenna I used, but I've set up an indoor bipole style 'T' and the signal meter is almost at its end stop on about 10 stations, with the sound clear as a bell, and the stereo light isn't lighting.

Naturally I assumed it was the bulb, but I tested this and it works.

Back to the listening test and I can tell it's not a stereo output via flicking between stereo and mono. There's no separation.

I've tried different pre-emphasis setting to no avail (whatever that means ;-) ).

What could the cause of this be? Any ideas? I hope it's not the MPX IC... Could it need an alignment? I know little about radio, unfortunately.

Maybe I should start a new thread under Analogue?...

Thanks

Stuey