80's Technics Integrated Amps

AK made me do it: my 'new' Technics SU-V909

Hi, everybody. I'm new here in the sense this is my first registered post, but I've been lurking for a while because AK is a wonderful source of screening data for prospective purchases on the Bay or CL.

As an original owner of Technics gear from the "UPS Brown' era (SU-8080, ST-9030 & M85---all still working), I have a high level of respect for the brand, its build quality and sound.

Recently, I set out to acquire an 80+W integrated amp to power a pair of late-seventies Lab Standard (house brand of a Manhattan dealer) 4-way speakers with 15" woofers that had been collecting dust for 17 years. My search of eBay turned up the usual suspects, some of which likely required repairs/refurbishing.

Among the Technics amps on offer was a SU-V909 which was described as 'lights working but no sound'. I immediately scanned the photos included with the listing to see if the 'Computer Drive' and 'new class A' logos were also illuminated as they should be.

Seeing that they were not, I concluded--based upon hours of late-night reading of AK posts on just the same problem--that salvation might be obtained at modest cost via replacement of the two offending $3 lamps/leds.

Hoping* this to be the case, I won the auction (actually beat a sniper!) and am gearing up to attack the problem with the aid of a friend (a former Sony Music engineer with better soldering skills).

Any technical and moral support offered by AK members would, of course, be much appreciated.

Thanks for the opportunity to participate.

*a word best used in churches and synagogues
 
Welcome aboard! AK has made most of us do lots of things...:para:

Good luck with the new amp. Awesome!
 
Keep us posted... I know these amps... Remember getting that light bulb conclusion when the amp was on the other side of the planet...

You'll like this amp
 
Glad to see you on the case, SVI2004A!

Your earlier posts on the subject were part of my late-night reading.

I should receive the dingus in about a week and will give everybody a heads-up when I get a look under the hood.

Thanks for your interest!
 
It's all good

I am betting on it being the lights. Amps of that era have this issue as the filaments get brittle and often after moving the amp, they let go.

Why Matsushita decided to use the bulbs as a volt drop is beyond me... In the 303 505 and 707 they didn't
 
The Eagle has landed...

The SU-V909 arrived yesterday. First impressions: (1) whatever good stuff is inside, it sure weighs a lot; (2) under the hood, the engineering complexity of the layout makes my SU-8080 look like a beginner's design; and (3) this thing is dirty like looking at the backyard through a screen door.

More critically, after powering up, I confirmed that the lamps behind 'Computer Drive' and 'new class A' on the front panel were not working. I have yet to attach a program source and speakers or head phones, but suspect no output will be forthcoming.

A couple of questions: (1) any recommendations as to a good spray cleaner that can be used without detaching the boards from the chassis? (or, more generally, suggestions for cleaning* 30-year-old amps?); and (2) for those who have replaced the offending lamps on their units, what are the specs/serial numbers for these items?

I'm happy to report that my soon-to-be house guest the former Sony engineer has good soldering skills and is not afraid to use them here. He won't arrive til the 20th, so I should have time to get the replacement lamps and perform a bit of spring cleaning beforehand.

Will keep the board posted as we move forward.

Thanks in advance for your suggestions/comments!

*including discharging the capacitors
 
You will want 3x 12V 55mA axial bulbs 3 or 4mm tube diameter

2for the new class A logo, one for computer drive

These amps don't hold the charge in the resivior caps for long... Idling current discharges them.

There are various threads on here about cleaning switches etc.

Myself I use CRC CO contact cleaner, video spray. Have some faderlube for pots.
 
Thanks!

Is the CRC an evaporative cleaner that can be sprayed indiscriminately without fear of harm to anything?
 
Inside the belly of the beast: SU-V909

A break in the weather allowed me to spray-clean the boards outdoors with CRC QD Contact Cleaner (I'll use Deoxit on the pots).

Laboriously disassembled the front panel to get at the burnt-out 'Computer Drive' and 'new class A' lamps. Noticed some missing screws but no signs of any DIY tampering.

The lamps are soldered to a board that appears to be pressure-clipped to a plastic pigeon-hole assembly which channels light to the front panel. The pigeon-hole assembly is not releasing when the clips are pressed.

Is it possible to replace the lamps with the assembly still attached to the board? (Looks like it from here.) At this point, I'm a little antsy about forcing anything.

Lined up a supplier of replacement lamps and will have some on hand for the arrival of Mr. Sony on Sunday.

Later.
 
Ahh yes.. To remove the pcb, you will need to desolder all the LEDs on the pcb.

Then board easily comes off.... You may want to put some sticky tape across the front of the cluster to keep all the LEDs in the right hole and polarity...

I highly recommend desoldering braid for things like this.

It's all straightforward from there
 
So you're saying we can de-solder the three offending lamps and replace them without detaching the entire pcb? All of the other (mini) lamps work.

Thanks again for your help.
 
I desolder all the LEDs then remove pcb grom the cluster... Then I change lamps on the open pcb. Then refit and resolder all LEDs
 
OK. Learned today that one of the lamps is still good, but should probably replace all three when I have the chance. Unfortunately, the electronics dealer who thought he could help does not have the lamps. I'm now scrambling to find a supplier/dealer somewhere in North America. A British firm named RS Components with distribution in the U.S. sources them from an Asian firm, but they aren't expecting a shipment 'til March.

Ah, the joys of owning vintage gear!
 
Just found some like-kind replacements at Candela on the West Coast. Should have them in a week or so. Their MOQ is 10, so if any AKers need a few, respond here.
 
Close, but no cigar...

Replaced the three axial lamps. Adjacent diodes are good. Decided to test fire the amp with a tape source and my HD-414s. Eureka! Computer Drive Christmas tree works fine and sound is good to phones.

Connected my Polk S4s for the acid test. Powered-up the amp without engaging the speakers. Once again, Christmas tree sequence executes properly and Computer Drive is engaged.

When I punched in the speakers (with Volume at 0), however, I heard a loud click and the Computer Drive and newclassA lights went out. No sound to speakers when I advanced the volume.

Give it to me straight, Doc. What's the diagnosis?
 
Could be tap select relay...

Is there voltage present where it should be? The fact the new class A light went out is interesting.
 
The plot thickens...

Shifted the speaker cables to the 'Remote' binders and was able to get sound. Does that 'exonerate' the speaker-protection relay?

I will examine/clean both sets of posts today. Could simple corrosion/oxidation be the problem?

Thanks for your help!
 
I mended a couple of Technics amps from the eighties recently. If you have a channel that cuts in and out it make be the coil wire on tbe relay broken. Using the remote or second set of speaker terminals will get around this as there is another relay controlling the second set of speakers.

Current Technics amps include a Technics SE-A1, SU-V90D and SU-V560. Did have an SE-A100 and SU-A200.
 
Has your amp been on shrooms?

New class A light dropping out is power supply related or blown bulbs... This will stop the ICQ controller from engaging output relay.

If all is well on remote speakers.... Your new class A lights etc will be lit... Fault will be main speaker switch
 
Sequencing is the key

IF the speakers are selected before power-up, the Computer Drive will boot through and the amp will function normally. If either set of speakers is selected after the Computer Drive boots, the Drive will disengage, effectively disabling the amp.

Hard to believe this is normal.

Currently driving my Polk S4s (measured at 4 ohms impedance) nicely. Will fire up the 4-way boomers this weekend.
 
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