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Speaker relays

Hyperion

Hyperion

Roobarb & Custard
Subscriber
I have become aware that speaker relays may be a hidden cause for concern in our cherished vintage pieces. I was always slightly puzzled when various AK restoration experts would announce that they had changed the speaker relays. I always believed that they had inspected the relays and decided to change the relays based on visual observation of pitted contacts. I was thinking, "how can they get pitted contacts when the contacts should be closed when the amplifier is playing, and open at any other time when significant currents might be able to flow". The speaker relays shouldn't be subject to drawing an arc when opening, (causing contact damage), except on the rare occasions when there is a fault, but it seems there is another failure mode. :idea:

So with the very recent BA-F1 restore, I removed one of the relays and had a close look, no pitted contacts but I noticed an unusually wide actuation distance compared to a new relay, (& no NC = normally closed) contacts - not that unusual. So I decided to energise this relay and measure the contact resistance - WOW - you could have blown me over with a feather, three out of four contacts showed resistances in the KΩ region! So then I got a brand new, although it had been in a parts drawer for a few months, MY4-02-DC24 relay (i.e. 4 sets of change over contacts), and tried that. Surprise! one contact pair showed a high reading varying a lot but less than 100Ω - cover off, one squirt of deoxit and fine, all four contacts then showed less than 0.1 Ω.

So I went back to the old BA-F1 relay, cover off, squirt of DeOxit - no change, tried actuating the relay multiple times (for 'wiping' action), and still the same. There must be a very thin film of oxidisation on the contacts which the tiny voltage/current from a digital multimeter on Ω range can't break though. The BA-F1 got a pair of replacement relays, checked for contact resistance, the new ones sound much less 'clunky' :) - Oh and another thing, the coil resistances were 50Ω different on the old relays, (another reason to change), but exactly the same on the new ones. :thumbsup:

Lesson learned, while previously not having been on my 'hit list' of items important to change, although I always visually checked the contacts, speaker relays are going to be included from now on. :) :music:
 
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Although I never measured old relays have had several with obvious contact deterioration over the years. This is another one of those as long as you are this deep in the rebuild anyways change the relay items for me. Good to know sir.
-Lee
 
Great post! I think they coat the relay contacts with silver b/c even silver oxide conducts well. Problem is, it's a thin layer that wears off... Thanks for that info.
 
this is probably just one form of corrosion from being around. like dust there's probably
some low percentage barriers being deposited on all surfaces.

I used to remove and re-insert all connects, speakers and RCAs, with a twist to
break the corrosion about once a month when I lived in a super hot clime.
heard the difference.

some have suggested pulling a strip of paper through the relay contacts wetted
with de-oxit.

this is a great tip. probably the first thing to check when protection doesn't work.
 
If I wiggle a relay and it causes drop outs, I pull it and inspect it. If the contacts are not pitted or worn through, I pull the spring and separate the contacts. Then I polish them with an erasure. If they look all nice and shiny I reinstall it and wiggle it while the unit is playing. If all good, it stays.

That said, I replace them on full rebuilds.

As far as how they get pitted, I suppose there are those that power up and down with the volume up. If music is playing when this occurs, there is voltage and could be a small spark. Over years of this practice, I can see the contacts pitting. Also, if the DC offset is high.

Rob
 
Correct. The amps DC is still settling down after the relay closes with most amps. User tech tip. If you want to keep your relays clean, and if you have the option, use your speaker switch. Wait for the relay to click, then turn on the speakers. Reverse for power down. This keeps the relay contacts in a dry state during actuating.

The BA-F1 uses all 4 contacts paralleled, with a MY4 relay for each channel. How it should be done.
 
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Anyone have any pictures of some of the relay's that exist out there any manufacturer, and pictures of the degradation or oxidation?
 
Harvestor said:
Anyone have any pictures of some of the relay's that exist out there any manufacturer, and pictures of the degradation or oxidation?
Click to expand...

Here are some shots of the relays from my Revox PR99. Inspect the 2nd and 3rd last pics in that post which show black, and then clean, contact pads (the tiny bits right at the very end of the arms). Sometimes the relay contacts don't mate well after a lot of use and it's just a matter of bending the arm and reassembling. If you see black stuff (carbon from arcing) on the contacts, that needs to come off. This is done by soaking a piece of paper in deoxit and using said paper as 'sand paper' (typically you can put the paper between the contacts, hold the contacts closed, move the paper around and clean all contacts in one go. continue with fresh paper and deoxit until pads are clean and no discolouration shows on the paper); I have also had success with ultrasonic cleaning, but always had to finish off with the paper technique.

It is important to not use actual sand paper of any type; I see emory paper/sand paper recommended all over the place. (a) you want the surface to be as flat as possible, even on a microscopic level, to maximum electrical contact and (b) sanding makes the arcing and build up worse and your black carbon comes back very quickly after using sand paper. Much of the advice that relays must be replaced is built up from people improperly cleaning relay contact and accelerating carbon rebuild-up . Relays that are pitted become coated with the black stuff again faster as the irregular pitted surface accelerates arcing and build up (type of corona effect (lightning rod) where electromagnetic potentials are enhanced near surface of high curvature (like tips of pits)). You can not easily see the pitting with the naked eye. I used to use fine grit sand paper and within days, weeks or months, the relays would go bad again. Since I have been cleaning relays with deoxit soaked paper, the majority of my relays have not given trouble again.

I do not replace relays as a rule; I inspect them and make a decision. Note that my stance has been formed working on units that mostly don't have good ready-to-go replacements available; if a replacement is readily available and it doesn't require butchering your unit to make it work/fit, sure, I would probably change my tone and just replace as a rule... but I haven' reached that point yet because of the model i tend to work on.
 
ManyMoonsAudio said:
I replace them in everything that has one. I have to really. I cannot risk having something shipped back to me because of a dirty relay.
Click to expand...

I should add that I only service my gear for my own personal use, so if I have a problem later it's not a big deal for me to clean again or replace at a later date, but if I was servicing other people's gear commercially, for sure I would agree with replacement where possible.
 
I have replaced mine on my ba3k's ba2k, ba5k. They were not pitted but a bit tired. The deoxit cleaning did not fully revive them. Actually under a magnifying glass they looked more than tired. A bit burned up , black deposits that I could not get rid of. Changed them and , piece of mind. On the other hand , both my BIG G's seem to be fine. Haven't yet checked the B2301, B2302 to see what is going on in there.
 
Back when they were $5, I just replaced them automatically. Now that they are $12, I pull the cover and clean the contacts with Brasso or Flitz (no abrasives) if they aren't pitted.
However, if I'm doing a full rebuild for a paying customer, I just install a new relay unless it's something special.
 
The frustrating thing is that solder lug relays are still around $6, while PCB relays are nearly double that. In the grand scheme of things, $6 ain't ****. But it's still annoying.
 
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