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Bypassing relays in receiver.....Onkyo TX8500

z-adamson

z-adamson

Addicted Member
I am beginning to wonder if it would make sense to bypass the two relays in my Onkyo TX8500.

One is for speaker protection and the other for keeping nasty noise out of the speakers at turn on and turn off....I think.

The idea crossed my mind that I could bypass the relays and use a on/off switch inline with the speakers. This way I more or less "become" the relays. I control when the speakers are protected. The speakers are last on and first off. I am OK with this added inconvenience if the receiver becomes more reliable. Nobody will be using this receiver but me.

Good idea? Bad idea?
 
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z-adamson said:
Good idea? Bad idea?
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Bad idea - One day it will develop a fault, you'll hit the switch, and blow up your favourite speakers.

Is this idea a 'permanent fix' instead of getting those relays working properly - what is stopping you do this?

You know that the inrush relay is saving your power switch from wearing out prematurely? - as this is partly what it's there for - how do you plan to deal with this?
 
Well, I dunno. Just a thought.

I have other amps that work well that don't have any relays, ie hafler dh200.

The relays are working properly, but they are 40 years old and I thought they may develop a fault sooner than later. Bypassing them means no more relay related fault. I am in the middle of a restore and I felt that bypassing them may make sense.

My other two options are leave them or find replacements. Still no luck on replacements. So.......bypassing them looks tempting.
 
z-adamson said:
Still no luck on replacements.
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I can't believe nobody knows the details of modern replacements for those relays - Onkyo isn't that well represented here, but somebody MUST have replaced those relays before!
z-adamson said:
So.......bypassing them looks tempting.
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May I respectfully say "no it doesn't" - they are part of the design of the unit - and are not only safety related, but also their correct operation contributes to how good the receiver can/will sound. (especially if the alternative is some hokey switch to short them out!)

My personal opinion, you may as well not bother to do any more work on it, and any you have done up to now is wasted, if you are going to be tempted with this very poor idea of yours. :(
 
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Hyperion said:
I can't believe nobody knows the details of modern replacements for those relays - Onkyo isn't that well represented here, but somebody MUST have replaced those relays before!
May I respectfully say "no it doesn't" - they are part of the design of the unit - and are not only safety related, but also their correct operation contributes to how good the receiver can/will sound. (especially if the alternative is some hokey switch to short them out!)

My personal opinion, you may as well not bother to do any more work on it, and any you have done up to now is wasted, if you are going to be tempted with this very poor idea of yours. :(
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Geez, all I have done in relation to this idea is ponder it. Work up to this point has been limited to replacing caps. Being tempted by this idea does not make all the recap work a waste. Could you explain that one a little? I am trying to understand your perspective as to why the recapping I have done is now wasted because I thought about bypassing relays.

Buuuuut, point taken.

Bypassing relays is now off the table.

Thanks

Z
 
z-adamson said:
Could you explain that one a little?
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What you were thinking of here was such a monumental hack to what is actually a very nice piece, that to do it would be total and utter sacrilege. How were you going to mount this switch? maybe remove the input selector switch (if it even has one?) and mount this shorting switch in the hole thus vacated? - then select inputs by connecting together croc-clipped leads !?! - I mean what's next? :yikes:

I spent a good 45 minutes last night - on your behalf - searching for the answer to this problem, but unfortunately I couldn't come up with an answer. I did find a picture of the TX8500 protection relay online but no other information. Other than a half remembered thought that the TX4500 may have used the same relays and searching on that might yield some results.

You must be able to mount even the wrong 'physical' type of 'functionally' correct replacement relay inside the case of the receiver? Or alternatively, use the Sansui relay list (linked earlier) as a look-up for commonly used relays. And by using the data sheets for those relays and carefully measuring your relays, come up with replacements - then you can be a hero and tell us what the replacements are. :)

Sorry I couldn't be of more assistance other than pouring ice cold water on what you have thankfully realised is a very bad idea. :)
 
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I'm a big fan of protect relays on direct coupled amps. It just makes good sense. I have one big DC amp with no protection relays and honestly it makes me a little nervous. One of the things I've always wanted to do was add that, and I think if I start using that thing more it will be done. My other SS amps without relays are cap coupled, and those you really don't need relays for. I won't tell you I like the thump they make when powering on/off though.


Worst case, if you can't find a direct match, a function match as Hyperion talks about would do fine. I've done that on things before. Match the coil and contact specs, mount the relay to a small piece of circuit board, attach it to the chassis someplace, and run wires from there to the main board were the original relay lived. Not quite as clean as a drop-in but sometimes you do what you have to do.
 
Hyperion said:
What you were thinking of here was such a monumental hack to what is actually a very nice piece, that to do it would be total and utter sacrilege. How were you going to mount this switch? maybe remove the input selector switch (if it even has one?) and mount this shorting switch in the hole thus vacated? - then select inputs by connecting together croc-clipped leads !?! I mean what's next?

I spent a good 45 minutes last night - on your behalf - searching for the answer to this problem, but unfortunately I couldn't come up with an answer. I did find a picture of the TX8500 protection relay online but no other information. Other than a half remembered thought that the TX4500 may have used the same relays and searching on that might yield some results.

You must be able to mount even the wrong 'physical' type of 'functionally' correct replacement relay? inside the case of the receiver. Or alternatively, use the Sansui relay list (linked earlier) as a look-up for commonly used relays. And by using the data sheets for those relays and carefully measuring your relays, come up with replacements - then you can be a hero and tell us what the replacements are. :)

Sorry I couldn't be of more assistance other than pouring ice cold water on what you have thankfully realised is a very bad idea. :)
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I don't think we are 100% on the same page.

My idea was this......

Install jumpers where the relays are. Make it as though they are closed all the time.

THEN......set up a 4 pole toggle switch in line with the speakers, outside of the receiver. This toggle becomes the relay. Speaker wire in, speaker wire out.

This is what I meant when I said this...

"The idea crossed my mind that I could bypass the relays and use a on/off switch inline with the speakers"

At no time was it in my plans to come up with a switch internal to the receiver. I would make an aluminum box on my CNC system, mount the toggle there. Set the box next to the receiver. Speakers on last and off first.

Again, if the idea is bad, then on to the next idea.
 
No, not a good idea.

Hyperion said:
Bad idea - One day it will develop a fault, you'll hit the switch, and blow up your favourite speakers.
Click to expand...

Not to mention, the one relay is your soft start relay, which helps limit the in-rush current when the caps and transformer first charge. Bypass that and you'll burn up your power switch in short order, not to mention there is a possibility of tripping the circuit breaker for the outlet the receiver is plugged in to, especially if it's been powered off for awhile.

You never provided pictures of the relays that are in there, that would help greatly in figuring out what kind of relays to use. Based on the schematic I'd say a LY2 for the soft start and a MY2 for the protection, both 12VDC, but that's only a guess. A picture of the terminal side of both relays would do the trick.
 
That approach seems possible:

http://provodok.org/index.php?productID=3202

I'm not sure I'd opt for that particular item / relay (it's marked as 5A rated, but advertised as 7A ?), but the approach of mounting a socket + std relay looks possible. You'd have to check specific sizing & relay specs. to be sure, but this link appears to suggest it's possible.
 
mattsd said:
No, not a good idea.



Not to mention, the one relay is your soft start relay, which helps limit the in-rush current when the caps and transformer first charge. Bypass that and you'll burn up your power switch in short order, not to mention there is a possibility of tripping the circuit breaker for the outlet the receiver is plugged in to, especially if it's been powered off for awhile.

You never provided pictures of the relays that are in there, that would help greatly in figuring out what kind of relays to use. Based on the schematic I'd say a LY2 for the soft start and a MY2 for the protection, both 12VDC, but that's only a guess. A picture of the terminal side of both relays would do the trick.
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The relays are...

MAT2B
103R

RABK-2P

Both 12vdc

Not too worried about tripping the breaker. I run dedicated 30 amp lines to my gear. I am worried about the switch.
 
You have two threads maybe three? and talk about not being on the same page...

http://audiokarma.org/forums/index.php?threads/bypassing-relays-in-receiver-onkyo-tx8500.844255/
http://audiokarma.org/forums/index.php?threads/need-help-finding-two-relays-onkyo-tx8500.843875/

Some posts are same link and OP can change one solved problem after another but I'd say you're pretty green with some of your ideas that won't work. relays?? I'll simply ask can you pull them without damaging the pcb?
safety here is always recommended and basics are checking obvious stuff first and plan on caps etc... If you want to keep experimenting and dreaming.. then don't post back as others need help, too.
 
z-adamson said:
My idea was this......

Install jumpers where the relays are. Make it as though they are closed all the time.

THEN......set up a 4 pole toggle switch in line with the speakers, outside of the receiver. This toggle becomes the relay. Speaker wire in, speaker wire out.
Click to expand...

It's not only the speakers you're protecting, it's the entire circuit. No throughput to those just keeps any transients from popping cones, but there's a lot of little sensitive bits inside the receiver that don't take too kindly to that sort of thing.

So ... unless your reaction times can be measured in milliseconds, I'd pass ...

(and IMHO no disrespect intended really - we're all just trying to point out the dangers)
 
Binkman said:
You have two threads maybe three? and talk about not being on the same page..
Click to expand...

I have way more than three threads on here.


Binkman said:
I'll simply ask can you pull them without damaging the pcb?
Click to expand...

Yes. I am capable of removing the relays without damaging the PCB.

Binkman said:
If you want to keep experimenting and dreaming.. then don't post back as others need help, too.
Click to expand...

No experimenting or dreaming has taken place, nor will it take place. All I did was think out loud about bypassing relays, which I have done several times with great results. This was in a preamp though, not a receiver. The relay in the HK725 preamp is bad every time (I have 6 of them), replacements are unavailable so I bypass every time. All I have to do remember that amps go on last and off first. A few of the HK725 preamps that I got already had the relay bypassed so clearly I am not the only one doing this with the HK725. It simply occurred to me that something like this may work with this receiver. Turns out I was wrong. Thats why I asked first. That is what this forum is about, right?

Good day,

Z
 
z-adamson said:
I have way more than three threads on here.

Z
Click to expand...

And that's the issue...you've separated all your questions into separate threads, yet they are all regarding the same receiver (I’m just talking about the threads regarding it BTW, not ALL the threads you've ever started). :D

You could have had them all lumped under one thread titled “Onkyo TX-8500 Rebuild” or some such title. Then, as questions arose, they'd all be answered in one place. This also helps future folks find the info if they're also doing a rebuild. Much neater than scattershot all over AK.
 
UPDATE:

Problem solved.

I bought a pair of MY2-02-DC12 Omron relays. AK member Avionic indicated that my old relays resemble the MY2 relays very much, so with nothing to loose and everything to gain, I bought TWO of them.

The MY2-02-DC12 relay was a direct replacement for the MAT2B 103R relay.

The MY2-02-DC12 relay will work to replace the RABK-2P relay, but it will take some extra work. The RABK relay has built in bracketry so that it can be bolted to the PCB then have wires soldered to the leads. This relay does not get soldered to solder pads as is typically the case. Using the MY2 in its place requires some kind of bracketry to be made. Beyond the bracketry, it is the same relay.
 
z-adamson said:
The MY2-02-DC12 relay will work to replace the RABK-2P relay, but it will take some extra work. The RABK relay has built in bracketry so that it can be bolted to the PCB then have wires soldered to the leads. This relay does not get soldered to solder pads as is typically the case. Using the MY2 in its place requires some kind of bracketry to be made. Beyond the bracketry, it is the same relay.
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Would a flange mount work better
Look at page 19 of this spec sheet.
https://www.mouser.com/datasheet/2/307/my_ds_e_7_3_csm59-940997.pdf
 
z-adamson said:
No, the mounting flange needs to be on the other end of the relay.

The flange needs to be at the end of the relay housing nearest the leads.

Unless I am looking at it wrong, the pic shows the flange at the end opposite the leads.
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How about using the old relay housing and replacing the internals with a new MY2 relay with quick connect pins rather than PC pins. I've done that before on a pioneer receiver.
 
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