From: Bob Blick <bobblick@outlook.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Tue, 28 Apr 2020 12:32:30 -0700
Subject: Re: [EE] Seeking audio relay advice
Thread-Topic: [EE] Seeking audio relay advice
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Hi Sean,

Reed switches were a just a suggestion in one of the responses. They are su=
pposed to be filled with inert gas, like the Aromat/Panasonic HB2E series o=
f relays that Phase Linear was using as replacements for the original unsea=
led relays.

Best regards, Bob
________________________________________
From: piclist-bounces@mit.edu <piclist-bounces@mit.edu> on behalf of Sean B=
reheny
Sent: Tuesday, April 28, 2020 12:04 PM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Seeking audio relay advice

Bob,

Why are you so convinced that reed switches wouldn't suffer the same
problem? It's still a contact and it depends entirely on the material of
the contacts. The original relay sounds like it had gold-plated contacts
which I think should work with dry switching - at least until the gold
wears off. Mercury-wetted is probably the best solution. Another would
probably be to introduce a DC bias current (although I know you don't want
to alter the design of the amp).

Sean


On Tue, Apr 28, 2020 at 2:26 PM Bob Blick  wrote:

> Thanks everyone who replied and for the suggestions. I decided to take th=
e
> chance and for $26 I have 20 HB2E-DC24V relays coming from an Aliexpress
> vendor. Although I'm sure what will show up will be relays, whether they
> are counterfeit or used is unknown at this time. The picture and
> description seem correct.
>
> As to the question about the failure mode, it's a contact issue, and the
> symptoms are distortion, noise, and signal dropping out. Cycling the tape
> monitor and input selectors clears it up for an annoyingly short time. Wh=
en
> I originally got the unit I popped the tops off the relays(this unit has
> the original Omron unsealed relays) and squirted Cramolin, that worked fo=
r
> a month or so.
>
> This is a preamplifier, so the signals are all low level audio under 2
> volts AC, and very low current. So it's the textbook low current dry
> contact problem.
>
> I love the idea of hacking the relays apart and putting reed switches int=
o
> the the original magnetic structure. Maybe I'd try it if I didn't have to
> do it for 13 relays, each requiring two SPDT reed switches!
>
> In 2 months when the relays finally arrive from China I'll post a reply
> with what showed up and if they work.
>
> Cheerful regards, Bob

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