Sansui AU-717 - ALPS Potentiometer crackly...

[the record spot]

My current amp has one of these (sounds like a posh volume control if you ask me, but I'm a dullard when it comes to electronics - anything beyond wiring a plug and turning stuff on and off is the Twilight Zone for me) and a local audio repair guy gave the interior a clean the other week. The right channel had been a little crackly and though it has improved, it occasionally drops the same channel and I need to set the speaker selection knob to "off", turn the volume knob up and back down again and that seems to cure it.

The problem doesn't lie elsewhere - tried swapping the interconnect round and it's not the CDP (sorry Ash, that damn mechanism keeps spinning 20 months on!). When I collected it the other day, the guy in the shop was clear in saying he didn't tinker with the ALPS interior as it was a good standard one, not to be messed with etc.

Here's an interior shot of the amp, the top covered area sits behind the fascia, so this is where the volume and other front controls are held.

Two things for those who may know: are ALPS controls trickier to service and what are the issues in getting round this kind of problem? Most other sites seem to feel volume knob crackle is a fairly easy problem to resolve, however, my repair guy reckoned against using DeOxit or the like on it due to the residue it apparently leaves behind.

So, any suggestions guys? As I say, it doesn't happen often, but it'd be nice to have fixed.

 

[Andrew Everard]

Yes, a potentiometer is a volume control. The problem sounds like dust or corrosion on the 'tracks' of the pot, given that turning it up and down a few times reduces the problem - you're literally sweeping the tracks, and wiping them clean.

I'd agree with your repair guy; the best solution would be to try to source a replacement pot.

 

[Anonymous]

there is a way and think it's called 'scrubbing' .... don't know the exact procedure, but if memory serves me right, you rapidly turn the control several times .... best way is still deoxit (there are several types so google)

there is a vintage sansui forum that will give you all the info .... in google search for vintage sansui forum ... post your question there and you will get the answers ....

find it strange that the guy who serviced your amp never sorted that?

 

[the record spot]

Thanks Andrew - do you know if there's a lot of them around out there? Appreciate it's hard to say and the amp dates from November 1977 (going by the code on the serial number) so it might be tricky to land one for that era?

Also, who/what were ALPS? A manufacturer or just another type of volume control, if that makes any sense?

 

[Andrew Everard]

ALPS was, and still is, a maker of high-quality components, probably best-known in the audio field for its potentiometers. Some very good amps still use ALPS pots: it's one of those things PR people tend to put in press releases as a badge of quality when describing products.

The AU-717, IIRC, uses a unique four-gang pot with some loudness functionality as well as volume control, and I gather replacements are no longer available. That means either sourcing a volume control from another 717 which has been trashed in some other way, although of course this carries the risk that it may be as noisy as the one you have now, or getting someone familiar with servicing potentiometers to strip down the one you have and attempt to service it.

Either way, I think it could be tricky/pricey, and you may settle for putting up with what you've got.

 

[the record spot]

dim_span:
there is a way and think it's called 'scrubbing' .... don't know the exact procedure, but if memory serves me right, you rapidly turn the control several times .... best way is still deoxit (there are several types so google)

there is a vintage sansui forum that will give you all the info .... in google search for vintage sansui forum ... post your question there and you will get the answers ....

find it strange that the guy who serviced your amp never sorted that?

Ah, he did, or at least he opted not to use DeOxit as it apparently leaves a residue behind that could exacerbate the problem. He used an alternative which doesn't and at the time of writing this, it's been absolutely fine this morning. Even the crackle I was getting around the 11 o'clock position has reduced significantly) - in practice, it never goes anywhere near this level; way too loud!

Thanks for the other info though; handy to know - I did check out one of those which has an Exclusively Sansui subforum a few weeks back, so will revisit.

 

[the record spot]

Andrew Everard:
ALPS was, and still is, a maker of high-quality components, probably best-known in the audio field for its potentiometers. Some very good amps still use ALPS pots: it's one of those things PR people tend to put in press releases as a badge of quality when describing products.

The AU-717, IIRC, uses a unique four-gang pot with some loudness functionality as well as volume control, and I gather replacements are no longer available. That means either sourcing a volume control from another 717 which has been trashed in some other way, although of course this carries the risk that it may be as noisy as the one you have now, or getting someone familiar with servicing potentiometers to strip down the one you have and attempt to service it.

Either way, I think it could be tricky/pricey, and you may settle for putting up with what you've got.

Turns out, I've sourced one! A chap on another forum had a spare going which he's offered me. Ashley James no less, so a big thanks there. Even if the current one sorts itself out, it'll be useful to have the spare were the same problem to reoccur in future.

When you mention "loundess" functionality, is that referring to the Loudness switch on the fascia built into the same pot in some way? There's a bunch of switches on the front which usually sit at "off" as well as various tone filters at different settings which are bypassed by the tone defeat.

EDIT: thanks for the ALPS info and link too by the way, good to know the background.

 

[Andrew Everard]

Glad to hear you sourced a replacement. Yes, I think that's how the loudness function works, but it's ages since I've seen or used one of these amps.

Explanation here

 

[Blackdawn]

Ah, he did, or at least he opted not to use DeOxit as it apparently leaves a residue behind that could exacerbate the problem. He used an alternative which doesn't and at the time of writing this, it's been absolutely fine this morning.

Hi RS, Hows the Sansui? What was the name of the contact spray your technician used? Still going to sell the amp? Thanks

 

[Richard Allen]

Hi RS.

Try a propriotery switch cleaner. You can get at the tracks on an ALPI pot. dust and ***t can be cured by this without the cost of replacing the pot.

 

[the record spot]

Hi chaps, well, this old thread brings back the memories! The amp's working like a dream just now (touch wood) but yes, the plan is to shift it on at some point. Thanks to various things, but mostly my contract not being renewed when it was expected to be, my planned purchase of a Harman HK990 was cancelled after The Home Cinema Centre had taken delivery in the shop. It was waiting for me, but had to cancel (gutted). Luckily, they understood and were fine about it. The contract's been renewed, but £500 just went on some car repairs (typical!) and it's the tax year end so I won't be splashing the cash on anything major for a little while.

However, Mrs. R_S pointed out that she doesn't want a really massive amp replacing the 717, so a new DAC (possibly the Emotiva I've been raving about) might come in, but am considering my options just now. The new amp would be a smaller affair, but with the same power output or better.

 

[arnaud]

Hello
I got a au717 with sansui pre-amp down on the bench I discovered with horror That a carbon potentiometer tracks had been massacred (carbon track 5Kohms).
I think with another potentiometer alps 1090280 defect i can built a good.
If someone somewhere that I will be very happy to buy it, with shipping to France.
Best regards Arnaud.

 

[the record spot]

Bonsoir Arnaud,

It's funny you should bring this up. The potentiometer I mentioned above I still have somewhere, although the amp is long gone now. I never did use it. If you'd like to pay postage, I'll send it out to you at the weekend. Let me know if you want it sent on. No idea if it's the right one, but it is an ALPS pot.

 

[arnaud]

hello INCREDIBLE! I am very happy to know that you still have this potentiometer is unexpected for me.
A huge thank you for your proposal, I can pay the potentiometer and shipping with paypal or other ...
Best regards Arnaud

 

[the record spot]

Hi Arnaud, drop on eof the moderators a line, we can sort out your address off the main web page. I'll post it out on Saturday morning (I don't work near a post office during the week alas). Postage is fine, the original pot cost me nothing.

 

[arnaud]

I think I understand, and contacted a moderator, sorry my English is very bad, and with google translator is very ..... Approximate!
thank you and good evenin.

 

[the record spot]

No problem, I understand. I'll wait for the mod to send me the info.

 

[arnaud]

I have just find a way to contact by email the moderator and ask him to give my email.
I do not understand :help:
I communicate tomorrow after work:wave:

 

[the record spot]

No worries - if JD or one of the other mods is around, can you put Arnaud and I in touch. I can arrange to send this ALPS pot across to him then. Thanks in advance.

 

[arnaud]

Hello, have you my email ?

 

[arnaud]

I created a temporary mailbox, I think this is the only solution, thank, you to write to me: potentiometre@laposte.net

 

[arnaud]

hello,

please do not leave me, it's too cruel to me, if you have an ebay account (or a friend) you can put the potentiometer on ebay international and see my profil " arnaud1308" i am serious and not bad....

Whithout your potentiometer to my 717 is not repairable, this potentiometer is not standard, it is specific only for this model, is impossible to find an équivalence, help me ray:

best regard arnaud.

 

[the record spot]

Hi Arnaud, take it easy man. Please note I said before, this is an ALPS pot, but I don't know if it fits the 717. Happy to send it to you to try out but please understand it might not be a match.

 

[arnaud]

Thank you very much for your honest answer, if this is the right at the back it says the number 1090280, 150kohmsX2, 5kohmsX2, and this potentiometer possesses 5 floors (platic stacked blocks) and 14 connections.
I am very pleased that this is so, but if it's not that I will survive ....
Thank, good evening

 

[arnaud]

Hello,

you can see here on page n° 7 : http://www.cdkands.com/AU717-7.html

Good day