Watts speaker relay
- Thread starter v65magna
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It's not an original design by Don. Other people have made the same version since it was in the PL service manuals. You are right, the design is proven, but with my stash of relays that I got for free, I can get 10 relay PCB's made for $180. With common parts laying around I can build a relay PCB for about $20.
I'll stop sharing my ideas.
I'll stop sharing my ideas.
You new guys don’t see what someone like Don has done for the Phase linear community. All the manuals flying around the web all came from Don. Maybe you can build a board but it’s a bastard. You’ll pay the price later when you try to sell it. His stuff is the standard and it’s about time people recognized this fact. Pony up and buy some blank boards from Don.
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Don's board has also saved my speakers. But I dont see how stifling any attempt at innovation is in our best interest. It's another spinoff of the same basic design. And...it can be used on other amps, for that reason alone is enough for me to support it.
Glen, Don and I go back aways and I don't think he'll have a problem with this.
Magneto, I think it's natural to want to incorporate surplus goodies into something usable and applaud your efforts. I hate waste as much as anything. Glad you found away to make use of your surplus. Please keep sharing your ideas, perhaps in the future it's something we all can support.
Glen, Don and I go back aways and I don't think he'll have a problem with this.
Magneto, I think it's natural to want to incorporate surplus goodies into something usable and applaud your efforts. I hate waste as much as anything. Glad you found away to make use of your surplus. Please keep sharing your ideas, perhaps in the future it's something we all can support.
If arcing across the relay contacts is a concern, could we just use the Zobel RC Network (R1/C8 and R2/C9) positions and insert the components for a Snubber Circuit for "break" arc suppression across both sets of relay contacts?
Using a maximum (VO) voltage source of 80VDC for a PL400 and a (RL) of 8 Ohms as a load resistance,
the resistance of the RC snubber would be 1.2 Ohm and the capacitance of the RC snubber would be 24.15 uF. The resistor could be 2W and the capacitor could be 100V because the circuit would only be active momentarily when the relay opens under amplifier power.
Using a maximum (VO) voltage source of 80VDC for a PL400 and a (RL) of 8 Ohms as a load resistance,
the resistance of the RC snubber would be 1.2 Ohm and the capacitance of the RC snubber would be 24.15 uF. The resistor could be 2W and the capacitor could be 100V because the circuit would only be active momentarily when the relay opens under amplifier power.
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I'm not one to steal or take credit for anyone's IP. Quite the opposite. It looks like others have already made their own version too from the original circuit to meet their specific needs.
I came across the thread about the relay because I was finishing up my version of the speaker relay (and was looking for any more info out there before I finalized it) and noticed that Don mentioned the Form C configuration which is exactly what I am going to use.
Yes, I designed it for my stash of amps and my intent was not to sell or market it. Don can sell as many as he wants, I don't care about selling small PCB's for something like this.
As you mentioned, it is a way for me to use parts I have, plus I enjoy laying out PCB's. It is like therapy (yoga) for me.
I came across the thread about the relay because I was finishing up my version of the speaker relay (and was looking for any more info out there before I finalized it) and noticed that Don mentioned the Form C configuration which is exactly what I am going to use.
Yes, I designed it for my stash of amps and my intent was not to sell or market it. Don can sell as many as he wants, I don't care about selling small PCB's for something like this.
As you mentioned, it is a way for me to use parts I have, plus I enjoy laying out PCB's. It is like therapy (yoga) for me.
- Joined
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First of all, thanks to all for the nice comments. Yes, the P.L tech manuals I’ve shared have ended up on a few other sites. I didn’t write them and don’t have legal rights to them. I was fortunate to get approved as a P/L service provider in early 1984. That brought all of the service manuals that were available at that time. Eventually i’ll get my stagnant website updated and all of the manuals will be there for download. Is there a Wordpress expert out there?
Having repaired a boatload of 400’s, many of which were in P.A. racks, I developed the 400 board after researching tons of circuits and data sheets. This was partially due to economics as the number of 400s far out weighs the 700s. Blame Gibsonian for pushing me to do the 700 board. I’m not embarrassed to say I adapted the original P/L 200 design for use in the 700. It didn’t bother me when other people copied my 700 design.
At my day job I have access to all kinds of ice cube relays. I welded at least 40 relay contacts trying to find an R/C network that would protect the contacts from 80 volts DC. Nothing but failures. It’s no accident that most relay contacts are rated fo 30VDC and 250 VAC. Using the normally closed contact to short across the speaker acknowledges the difficulty of finding a suitable relay. For a good tech note on snubbers search for “quencharc” or PM me.
On a different note I was at the Saudi oil company Aramco last week in Jeddah, Saudi Arabia. It’s just down the road a ways from Israel. I originally considered a detour through Israel on the way hone. Previous experience in that part of the world said get out as soon as you’re done at the job site.
Having repaired a boatload of 400’s, many of which were in P.A. racks, I developed the 400 board after researching tons of circuits and data sheets. This was partially due to economics as the number of 400s far out weighs the 700s. Blame Gibsonian for pushing me to do the 700 board. I’m not embarrassed to say I adapted the original P/L 200 design for use in the 700. It didn’t bother me when other people copied my 700 design.
At my day job I have access to all kinds of ice cube relays. I welded at least 40 relay contacts trying to find an R/C network that would protect the contacts from 80 volts DC. Nothing but failures. It’s no accident that most relay contacts are rated fo 30VDC and 250 VAC. Using the normally closed contact to short across the speaker acknowledges the difficulty of finding a suitable relay. For a good tech note on snubbers search for “quencharc” or PM me.
On a different note I was at the Saudi oil company Aramco last week in Jeddah, Saudi Arabia. It’s just down the road a ways from Israel. I originally considered a detour through Israel on the way hone. Previous experience in that part of the world said get out as soon as you’re done at the job site.
Experimenting is always in order because there are compromises as others have stated. This is a starting point based on the following formulas:
1.2 Ohm 2W Arc Quench Resistance R(q) = V(t-arc min) / I(L)
and
25uF Arc Quench Capacitance C(q) = V(s) / {E(BDN) x V(co) x R(c)}
Where:
V(t-arc min) = Minimum T-Arc Plasma Ignition (12.00V assumed)
I(L) = Load Current - Resistive (5 Amps for 8 Ohm loads assumed)
V(s) = Supply Voltage (80V assumed for PL400)
E(BDN) = Dielectric Breakdown Field Strength (3.00 mV/m assumed)
V(co) = Contact Opening Speed (0.12 m/s assumed)
R(c) = Charge Resistance = R(L) + R(q), where Load Resistance R(L) = V(s) / I(L)
The RC Snubber is connected across the Load and not across the Relay Contacts because this would allow an additional path for current flow around the Relay Contacts.
This may prevent the Reay Contacts from becoming welded once. After that, the relay would not energize at the next Power ON due to the DC voltage being present on the Output.
1.2 Ohm 2W Arc Quench Resistance R(q) = V(t-arc min) / I(L)
and
25uF Arc Quench Capacitance C(q) = V(s) / {E(BDN) x V(co) x R(c)}
Where:
V(t-arc min) = Minimum T-Arc Plasma Ignition (12.00V assumed)
I(L) = Load Current - Resistive (5 Amps for 8 Ohm loads assumed)
V(s) = Supply Voltage (80V assumed for PL400)
E(BDN) = Dielectric Breakdown Field Strength (3.00 mV/m assumed)
V(co) = Contact Opening Speed (0.12 m/s assumed)
R(c) = Charge Resistance = R(L) + R(q), where Load Resistance R(L) = V(s) / I(L)
The RC Snubber is connected across the Load and not across the Relay Contacts because this would allow an additional path for current flow around the Relay Contacts.
This may prevent the Reay Contacts from becoming welded once. After that, the relay would not energize at the next Power ON due to the DC voltage being present on the Output.