Sound Technology 1700B and 1701A... busted!

P

PacificStereo

Super Member
Hi, everyone:

Does anybody have experience repairing the 1700 series of distortion analyzers from S/T? All three of mine (two 1700Bs and a 1701A) are now defective. None will null, and one has the weirdest-looking output you ever saw.

S/T wants a _fortune_ to repair one. And there is precious little info on them on the 'Net, which I find a little bit surprising. I am now DOA on things like FM alignment, which is not good.

Does anyone have any resources in this area?

Thanks.
 
My have to bite the bullet...

Any repair would require recalibration...With calibration Cert. equipment.
 
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I'd suggest contacting Tom Ishimoto at Northridge Electronics in SoCal. If anyone can help diagnose and possibly repair, it would be him.

You might also call Fred Longworth at Classic Audio Repair in San Diego and see if he might be able to help.

Sorry to hear about your trouble, I've been trying to get a set of Sound Technology gear for years now. Had a 1701 sent from Great Britain and it never arrived!! :tears:
 
If you have the schematic, you can swap the same op amp to isolate the defective circuit.
I did just that on my ST 1701A
Distorted output. There are quite a few NE5534 Op Amps inside. Just replace the op amp in the same socket.
There are 'self tests' that the user can perform. No need for expensive alignment unless its way off.
 
Look to the Vactrol LDR's (Light Dependent Resistors). I've replace a few. Also, those ganged switch assy's don't like pure DeOxit, you might try faderLube there as they get sticky.
 
When mine broke the first time it was the main pot on the front. The second time if was connectoritis on the main switch bank. The third time was strike 3, you are out!
 
Yeah, I have swapped several of the op amps around between units. Also, have someone at Clairex (they made the LDRs) working up a test procedure for the parts, which I have not received yet (need to E that guy!)

I've checked obvious things like the power supplies and such.

Does anyone have a manual for a 1701A? I have prints for the 1700Bs, but my manual for the 01 has vanished. The oscillator in the 1701A is different than the 1700Bs.

Will keep ya'll posted if I find the culprit(s).

As far as calibration goes, there's an alignment procedure in the manuals. And even if calibration is marginal- I don't need much precision. I don't care about being able to measure down to 0.001%- I'm more interested in the 1% range for FM alignments and that sort of business.
 
....I think I got some from Audio Research. They use'm in the SP-8 and SP-9. ARC uses them as mutes and things. Later, I found a source something like Digi-Key, but I don't remember now (Sorry). The important thing is to find a model that has a similar Rdark and Rled at some current. This will make sure that the system can control the LDR's resistance properly. The bummer is, when I first did this, I had to try different one's to see what was the best fit. Sound Technology just had their part number in the part list and not the generic.

Unfortunately I did not write down the part number that I ended up using (sorry No. 2). ....and these repairs were on units at shops I was working at and not on the 1701 that I've got now. I'll hunt around and try to find a source and post the link.
 
I had a 1700B on my bench back in '77-81. It was brand-new out of the box when I unpacked it. Had the auto-null low distortion and IMD options as I recall. anyway, the LDR opto couplers failed in it within the first year. Stopped auto-nulling in the low distortion mode, would keep trying but would not stabilize. I remember keeping a couple of those couplers in my bench drawer after that just in case... but that was 30 years ago.
 
Yeah, these are Clairex parts (and I am not where I can look at the numbers, right now) and they tend to fail. I have a suggestion for a sub from someone else, but again, I am waiting on a test procedure to see if the parts are indeed bad. And yes, Ed- I had the same thing. The first symptom was no null in lowD mode, though I have one where the oscillator is defective, making a very strange waveform.

I am going to tackle this nut fairly soon, so if/when I know something, you guys will, too. And of course, I do appreciate any and all suggestions!
 
Pac-man: Having just won an auction for a 1700B (which remains in crapshoot-until-it-arrives status as always with online purchased test equipment), I am interested to see the resolution of your ST DA repair issues.

Question: Casual Googling also turned up references to 'ugrade modifications' which seem to be Op-amp update subs to newerer-betterer ones. Anyone have comment and/or details on that concept?

PacificStereo said:
Does anyone have a manual for a 1701A? I have prints for the 1700Bs, but my manual for the 01 has vanished. The oscillator in the 1701A is different than the 1700Bs.
Click to expand...

Sorry this doesn't help you, but for anybody else looking for the 1700 A/B documentation:

The PDF manual for sound technology 1700B is available online right here:
http://www.pmillett.com/vintage_data.htm
 
PacificStereo said:
Heh. Almost bid on that one. :)
Click to expand...

I'll let you know if it was me or you that turned out lucky... :D

Actually I swore off buying TE on auction sites but somehow slipped off the wagon over the last month or so. At least my default expectations are "likely a piece of useless crap that was lied about" so I can be pleasantly surprised if not...
 
PAC - Any update on this project?

I just received mine and while the analyzer side seems to be working, the oscillator seems to have the usual bad LDR & VCR parts... Works OK in 'fast' mode but falls on its face in low-distortion mode. Basic voltages check out OK and troubleshooting chart points right to the 'usual suspects'.

Called Clairex today looking for a modern sub for the CL6014M, they were willing to be helpful on the phone but couldn't guarantee anything, waiting for a callback after he checks the old books. Will post whatever I find out here for future reference...
 
I'd be more than happy if any of mine worked in the fast mode...!

I've been working with someone at Clairex for months on these parts- no fruition yet. The last I heard, the gentleman was going to work on a test procedure for the 6014 parts so that it would be able to be determined of they are defective or not.

I've reminded him a couple of times, will do it again.

I have not torn into mine. The osc and measurement functions still work on two out of three boxes, which is what I need the most. FM alignment will have to wait until I have time to really dig into these things.

You think the VCR-1 FET is bad? Does anything besides the flowchart make you think that?
 
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