PL 700 Series ii power switch

Michael F

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#1
Hi All,
The power switch in my 700 series ii has shorted closed :( Is this a common issue?
A cursory search turned up a few replacement options for the 700B but nothing for the series ii.
Am I SOL?
 

George S.

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Michael F

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#6
Thats great news! Would a .1uf cap be ok tacked across the contacts?
Im a little surprised that the switched failed on an amp that has essentially been stored for the last 40 years.
Ill report back once repaired. Thank you kindly for all the replies and suggestions )
 

Michael F

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#8
Often the 700 ll only uses one set of contacts. You might find it’s just move the Leeds over to the unused set
That would be worth investigating.
I cant recall if the power switch has an unused section, but if it does I cant imagine why those contacts werent doubled up in the first place.
The amp is racked, in service and precisely calibrated for gain relative to another amp. Before performing any kind of repair, it would have to carefully removed and gain measured in order for it to be reset if the pot gets moved even slightly.
 

Michael F

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#9
That would be worth investigating.
I cant recall if the power switch has an unused section, but if it does I cant imagine why those contacts werent doubled up in the first place.
The amp is racked, in service and precisely calibrated for gain relative to another amp. Before performing any kind of repair, it would have to carefully removed and gain measured in order for it to be reset if the pot gets moved even slightly.
I found an old picture, it looks like there is indeed another set of contacts on the opposite side.
Why no capacitor I wonder?
 

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George S.

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#10
The 700 Pro I did the full WOPL on has a factory installed cap on the non wire side bridging the two sets of contacts. Not sure of it's value but probably 0.1 uF.
The switch is marked TV-5, does this mean 5 amps rating per set of contacts? I don't know.
I have taken the attenuator switches apart for cleaning, same switch is used in the PL2000 preamps. Power switch is similar construction. Best to do it in a large clear plastic bag (Jim's idea) as there are spring loaded parts. The contacts may be good, the issue may be in the spring loaded mechanism.
Later today I'll pull the top and bottom plate off the Pro and get you a good photo of that caps value and and orientation on the switch lugs. I presently have that system all tore down.
If it was me, I'd order that 6 amp C&K from Mouser and double the contacts with a cap.
And do the other amps also.
 

Michael F

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#11
The 700 Pro I did the full WOPL on has a factory installed cap on the non wire side bridging the two sets of contacts. Not sure of it's value but probably 0.1 uF.
The switch is marked TV-5, does this mean 5 amps rating per set of contacts? I don't know.
I have taken the attenuator switches apart for cleaning, same switch is used in the PL2000 preamps. Power switch is similar construction. Best to do it in a large clear plastic bag (Jim's idea) as there are spring loaded parts. The contacts may be good, the issue may be in the spring loaded mechanism.
Later today I'll pull the top and bottom plate off the Pro and get you a good photo of that caps value and and orientation on the switch lugs. I presently have that system all tore down.
If it was me, I'd order that 6 amp C&K from Mouser and double the contacts with a cap.
And do the other amps also.
Thanks for the reply. Is that Mouser switch a drop-in replacement ie no mods to either switch or chassis required?
 

George S.

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#12
Thanks for the reply. Is that Mouser switch a drop-in replacement ie no mods to either switch or chassis required?
Looks like it. If you go to the Ebay listing, he lists all the different units it's been used successfully on. Many of the units switches are no doubt board mounted like the switch I showed in the PL1000 S2 photo. Note the 700 is on his list, and his photos show a like replacement.
The mouser photo is not representative of course. But you can look at the data sheet.
Just be careful removing the old switch. Don't break off the bent over metal retaining tabs.
 
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#13
The 700 Pro I did the full WOPL on has a factory installed cap on the non wire side bridging the two sets of contacts. Not sure of it's value but probably 0.1 uF.
The switch is marked TV-5, does this mean 5 amps rating per set of contacts? I don't know.

a TV-5 relay/switch would be rated for 5A steady state current and 78A inrush, a TV-8 relay/switch 8A steady state and 117A inrush
 

George S.

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a TV-5 relay/switch would be rated for 5A steady state current and 78A inrush, a TV-8 relay/switch 8A steady state and 117A inrush
Thank you! Another one of those tips I need to print and post on the bench.
Looking at the data sheet I see no TV-X specs but a NE18 spec of 6 amps for the power switching section of the switch. Wonder if these specs are comparable. I'd research this but have a full days chores I need to jump on.
 

wattsabundant

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#17
I have a triac (solidstate switch) board that uses the existing switch (before it fails) as a low power controller to turn on the triac. The triac does the heavy lifting by handling the surge current. The existing switch lasts forever.

When I developed the circuit I recorded surge currents approaching 150 amps when the power switch closed. It's no surprise the switch fails.
 

mlucitt

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#18
When I developed the circuit I recorded surge currents approaching 150 amps when the power switch closed. It's no surprise the switch fails.
Inductive (transformer) inrush current will always be higher than non-inductive. Additionally, these switches are typically rated for current loads at 250VAC/100VDC. That means with our 120VAC mains power, you can double the current rating. Many switches are marked this way:
2A 250VAC
4A 120VAC
 

wattsabundant

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#19
Check and confirm the 100VDC rating. Most 250 VAC toggle switches are rated for 28 VDC. It's hard to stop the arc at 100 VDC with a load of more than a few milliamps..
 

mlucitt

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