Vintage synthesizers are sometimes cantankerous

Phil Hobbs

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Mar 31, 2015, 2:46:22 PM3/31/15

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I'm building a demo system in my lab, and not one, but _both_ of my
HP3325A synthesizers went flatline.

One had almost no output, missing attenuator steps, and distorted wave
shapes, and the other one flunked two of its three self-tests. Not good.

Turned out that ripping out the relay boards and cleaning the contacts
and connectors with DeOxit fixed both of them. (Score.)

(Thanks to the estimable Herbert Susmann for his web page.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

Gareth Magennis

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Mar 31, 2015, 3:38:08 PM3/31/15

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"Phil Hobbs" wrote in message news:551AEB7B...@electrooptical.net...

I'm building a demo system in my lab, and not one, but _both_ of my
HP3325A synthesizers went flatline.

One had almost no output, missing attenuator steps, and distorted wave
shapes, and the other one flunked two of its three self-tests. Not good.

Turned out that ripping out the relay boards and cleaning the contacts
and connectors with DeOxit fixed both of them. (Score.)

(Thanks to the estimable Herbert Susmann for his web page.)

Cheers

Phil Hobbs

--

Bugger, for a minute there I thought you were talking about a Minimoog or an
ARP.

Gareth.

Michael Black

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Mar 31, 2015, 7:21:09 PM3/31/15

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That's what I was thinking.

Michael

Ecnerwal

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Apr 1, 2015, 12:05:45 PM4/1/15

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In article <551AEB7B...@electrooptical.net>,

Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:

> (Thanks to the estimable Herbert Susmann for his web page.)

Ok Phil, I give up. I find some youtube comments and some google+
comments, but I don't think either would qualify as a web page bout
3325's, and herbsusmann.com seems to be a programmer with little
hardware (though he mentions a father who's an EE, so might be a son -
still, no 3325A info there.)

And no, I still haven't opened mine up for fixing yet. Find the last of
the tax paperwork and get that out of the way, then I might be able to
clear the decks for it (obviously I like it, I use it from time to time,
but it's not critical to my daily routine, at the rate I put off fixing
it. I'd just prefer to have some certainty I can get in and get out,
rather than have it half dis-assembled for a while and let the cats lose
parts of it for me...)

--
Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.

Phil Hobbs

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Apr 1, 2015, 12:53:29 PM4/1/15

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On 04/01/2015 12:05 PM, Ecnerwal wrote:
> In article <551AEB7B...@electrooptical.net>,
> Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:
>
>> (Thanks to the estimable Herbert Susmann for his web page.)
>
> Ok Phil, I give up. I find some youtube comments and some google+
> comments, but I don't think either would qualify as a web page bout
> 3325's, and herbsusmann.com seems to be a programmer with little
> hardware (though he mentions a father who's an EE, so might be a son -
> still, no 3325A info there.)
>
> And no, I still haven't opened mine up for fixing yet. Find the last of
> the tax paperwork and get that out of the way, then I might be able to
> clear the decks for it (obviously I like it, I use it from time to time,
> but it's not critical to my daily routine, at the rate I put off fixing
> it. I'd just prefer to have some certainty I can get in and get out,
> rather than have it half dis-assembled for a while and let the cats lose
> parts of it for me...)
>

It was just a comment, actually, but it's on his Google+ page.
http://tinyurl.com/myxsbpv

Jon Elson

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Apr 13, 2015, 6:57:24 PM4/13/15

to

Phil Hobbs wrote:

> I'm building a demo system in my lab, and not one, but _both_ of my
> HP3325A synthesizers went flatline.
>
> One had almost no output, missing attenuator steps, and distorted wave
> shapes, and the other one flunked two of its three self-tests. Not good.
>
> Turned out that ripping out the relay boards and cleaning the contacts
> and connectors with DeOxit fixed both of them. (Score.)
>
> (Thanks to the estimable Herbert Susmann for his web page.)

Yup, some years ago I rebuilt an HP 5100A synth (the original 1964 model
that took up about 2 feet of rack space.) It had hundreds of PNP Germanium
transistors in it, and about 15 of them had gone bad. I flipped it on eBay
as soon as I got it working, before any more transistors popped. Silicon
UHF transistors were a beautiful drop-in replacement. The rows of selector
button switches were also somewhat flaky.

Jon