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Is your unobtainium power switch worth $5 and an hour or so of your time?

Mentioned here and there in this thread is using external switches of some type to save unit power switch.

Be aware that the starting current still flows through closed contacts at the point on the sin wave the switch closes.

Any "gee I wish I hadn't done that" or major failure in the unit still has a chance of smoking you're vintage switch.

Yo pays yor money and takes yo chances
 
Bradbrews said:
This doesn’t seem right. The switch is only in the gate leg of the Triac. This leg is current limited by first the resistor in the circuit and then the Triac itself.
The data sheets list gate current.
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I just figured out there is a new process to quote a message since I last quoted one on AK:)
The message I thought I had quoted did not get quoted.

Bradbrews:
You are correct on a unit modified per this thread or similar.
There is no significant power switched by the vintage power switch.

I was reading / had read several posts to mean using an external switch of xx type instead of modifying the unit so transformer power does not go through power switch.
The implication being that if the make & break functions of the power switch are not used, there is no risk as long as the original power switch in in good condition.
 
Ahh- like when I use a power strip to turn the unit on instead of its own switch.
Yeah the power still flows through the switch then, but hopefully the arcs are in the power strip not the unit. However if the switch in the unit has high resistance it may still arc there too.
 
I have a Luxman r1120a in good working condition that I would like to do a mod to protect the switch. I have have tried to read through this thread however im confused on what to actually do. I also don't know how to read electrical diagrams very well. I cable of do the work I actually recapped a 1040 a while back.
Is there a kit with instructions like the recap kits or can anyone tell me what triac/parts to purchase and how to install for dummies, lol.
Thanks
 
nxs450 said:
I have a Luxman r1120a in good working condition that I would like to do a mod to protect the switch. I have have tried to read through this thread however im confused on what to actually do. I also don't know how to read electrical diagrams very well. I cable of do the work I actually recapped a 1040 a while back.
Is there a kit with instructions like the recap kits or can anyone tell me what triac/parts to purchase and how to install for dummies, lol.
Thanks
Click to expand...

I just had the same problem. Check out this thread, hopefully my description and diagram for dummies will help you.

SX-650 power switch repair - how to swivel the contact post?

Hi again Pioneer folks - my mint little SX-650 has the usual arcing power switch. I read many threads here on how to repair. This morning I was able to extricate the switch and got the rivets out. I see the round post is more like the typical 3/4 moon contact post. In addition to cleaning...
audiokarma.org
 
nxs450 said:
I have a Luxman r1120a in good working condition that I would like to do a mod to protect the switch. I have have tried to read through this thread however im confused on what to actually do. I also don't know how to read electrical diagrams very well. I cable of do the work I actually recapped a 1040 a while back.
Is there a kit with instructions like the recap kits or can anyone tell me what triac/parts to purchase and how to install for dummies, lol.
Thanks
Click to expand...
The R1120A looks to have a three way power switch. The triac would need to be placed on the side of the switch that connects to the transformer/outlets.


Screenshot (370).jpg
 
Hi - Just wondering if anyone might be able to advise - I'm planning on doing this switch mod on my Akai AA-1175, I had purchased a Q4025L6 on ebay for this job, and it wasn't particularly cheap, there doesn't seem to be many around here in the UK, I suspect they may be out of production ? There seems to be much cheaper ones in China, which I find suspicious .
Anyhow, just tried it today with a 100ohm gate resistor but no luck. Pulled the triac and put it on my component tester, which shows it is dead. I'm happy with the wiring and the resistor measures OK and the switch is good, so I'm guessing the triac was DOA ? Anyway, I'd rather not risk another one.

Now AI suggests that a BTA24-600CW will be a suitable replacement, they are certainly more available and about half the price of the Q4025L6.

But I'm not sure about the gate resistor value that I will need to go with it, AI suggests 270 ohms 1 watt will be good but I'm not sure I should be trusting AI twice in one day, and I'm a complete newbie to triacs, so could anyone in the know please sanity check this for me ?

BTW I'm in the UK so this is running on 240V supply.

Cheers - Dave.
 
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The Q4025L units are readily available, at least at Mouser, so no, not out of production. The BTA unit looks like it will work fine (& isolated package). I'm no expert either but I believe the 270 ohm resistor will be fine.
Not to beat the dead horse but buying components off auction sites isn't a great idea unless you know the seller is legit, either by personal experience or recommendations of others that have bought from them.
 
Hi - Thanks for your reply. Yes, I'm learning by trial & error that ebay stuff isn't always the best quality, but thanks for confirming the resistor value for me.
 
I use 100 ohm, 1/4 watt for the triac board I put in Phase Linear 700's. 270 ohm resistor shouldn't hurt. Too high of resistance and the triac will be slow to turn on (lots of microseconds) and could result in heating.
 
Mr Whippy said:
Hi - Just wondering if anyone might be able to advise - I'm planning on doing this switch mod on my Akai AA-1175, I had purchased a Q4025L6 on ebay for this job, and it wasn't particularly cheap, there doesn't seem to be many around here in the UK, I suspect they may be out of production ? There seems to be much cheaper ones in China, which I find suspicious .
Anyhow, just tried it today with a 100ohm gate resistor but no luck. Pulled the triac and put it on my component tester, which shows it is dead. I'm happy with the wiring and the resistor measures OK and the switch is good, so I'm guessing the triac was DOA ? Anyway, I'd rather not risk another one.

Now AI suggests that a BTA24-600CW will be a suitable replacement, they are certainly more available and about half the price of the Q4025L6.

But I'm not sure about the gate resistor value that I will need to go with it, AI suggests 270 ohms 1 watt will be good but I'm not sure I should be trusting AI twice in one day, and I'm a complete newbie to triacs, so could anyone in the know please sanity check this for me ?

BTW I'm in the UK so this is running on 240V supply.

Cheers - Dave.
Click to expand...
I wouldn't trust an LLM (AI) for circuit decisions or part replacements, especially for something connected to mains voltage. (Given how LLM's work--they don't have hard, database data, but a massive text vector store that drives generalized text prediction)

Mouser, Digikey, etc. all have hard database cross-references available with the"view similar" function for parts that are not in stock. Just check the boxes for all the major specs, including "isolated tab" for this application and they will show you reliable alternates. For this application, I would not trust parts from eBay.

If all I had were 270 ohms, I'd prob put two in parallel and get 135. But if I were ordering a triac, I'd get the 100ohm too.
 
Long story short, I've now got it working using a BTA24-600CW triac with a 270 ohm 1W resistor. (240 volt supply)

Original issue was the person who gave me the circuit diagram got it slightly wrong and it showed the gate triggered via the MT1 connection instead of coming from the MT2 (load side) connection, hence the original problem. First time I've ever used a triac so I'm on the learning curve.
So my original Q4025L6 was probably perfectly fine. Every day's a school day !

Thanks guys. - Dave.
 
thefragger said:
You still need a functional switch, however the working current across the contacts is cut significantly.
Click to expand...

i know this post is 10 years old but what are you guy's collective thoughts on contacts that were so pitted that i had to sand them with 1500grit?

it zeros out on the ohmmeter but there is no plating left, obviously.

edit: i need to add that i am asking about how long it will last with a triac.
 
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painttoad said:
i know this post is 10 years old but what are you guy's collective thoughts on contacts that were so pitted that i had to sand them with 1500grit?

it zeros out on the ohmmeter but there is no plating left, obviously.
Click to expand...
Might work fine for years or stop the next time called upon.

Only a new switch or redesign will solve the issue.
 
painttoad said:
i had to edit my post.

so i need to ask if your answer is based on triac or no triac?
Click to expand...
The triac should eliminate any further pitting due to electrical arc, since you're only switching milliamps, so you should get extended use, unless conditions accelerate corrosion (damp location, live near the ocean, etc.)

If you haven't sanded the contacts yet, can you burnish them instead?
 
50 Green said:
The triac should eliminate any further pitting due to electrical arc, since you're only switching milliamps, so you should get extended use, unless conditions accelerate corrosion (damp location, live near the ocean, etc.)

If you haven't sanded the contacts yet, can you burnish them instead?
Click to expand...
i've already sanded them. burnishing would not have worked. even if i had a burnishing file they were too pitted and the small contact did not want to come out and i did not want to break it. i couldn't have gotten a file in there.

the switch is mostly sealed and i live in il.
 
I think corrosion is your only concern. That really depends on the metal that is left, and how reactive it is.
The mechanical action will help to some extent, as will frequency of use.
It should help quite a bit if you coat the contacts with something like fader lube or maybe even dielectric grease.
 
Bradbrews said:
It should help quite a bit if you coat the contacts with something like fader lube or maybe even dielectric grease.
Click to expand...
i had this kicking around in a drawer?

would this work or do you have something else in mind?

i COULD use f100 or d100 if that was the better way to go.

20251215_082044.jpg20251215_082102.jpg
 
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