I am new here after lurking for years. I am making an attempt to rebuild one or both of my Parasound HCA-1205a. I have all the replacement caps on order as they are all leaking brown goo and the amps don't produce sound. As I was giving the individual amps a visual inspection, I noticed what I thought was a temperature sensor attached to the heat sink that also had the brown goo. This sensor is on Jumper 2, and the wiring diagram lists the part number as "TO-T95AR1U1" I can find no such part online. Anyway, the part has brown goo, but it may be adhesive. I am leaning away from that as it is in random places on all 5 of them. They are attached with a metal clip that screws into the heatsink, and thermal paste. I am attaching a few pictures.
Any thoughts on if these need replacing based on the brown stuff, and if so, what are they? Even Digikey tech support was stumped. Thanks
Any thoughts on if these need replacing based on the brown stuff, and if so, what are they? Even Digikey tech support was stumped. Thanks
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I stumbled across this via Digikey. At least it looks visually similar.
Can you use your ohmmeter to confirm it's a "mechanical" switch? Has it failed? Does any Parasound literature disclose the trip temperature? Assuming it's a simple thermostat, I assume you could substitute freely.
https://content.kemet.com/datasheets/KEM_SE0201_TRS.pdf
Can you use your ohmmeter to confirm it's a "mechanical" switch? Has it failed? Does any Parasound literature disclose the trip temperature? Assuming it's a simple thermostat, I assume you could substitute freely.
https://content.kemet.com/datasheets/KEM_SE0201_TRS.pdf
Thanks for the lead! I am looking into these. It is possible it that Thermal Reed Switch, case type. They contain "Thermorite," liquid. Described at Thermal Ferrite that that loses its magnetic properties at a certain temperature closing or opening a switch. That might explain the rust colored brown stuff if it leaked. If that is what it is, now I need to figure out the temperature.
Isn't that a thermal fuse ? Metal melts at low temp , others are just a bimetal and reset automatically.
A lot of amp thermal solutions use 70-80C as the magic #. I've seen 100C for old metal can output stages.
Ahh , this Parasound uses my favorite 2SC3519/2SA1386 (Sanken?). All my amps use these , 70C is what 2 of them have.
You could replace with a self resetting T switch.
Nice amp , simple complimentary (Leach DIY) stage with the JC fet's.....
OS
A lot of amp thermal solutions use 70-80C as the magic #. I've seen 100C for old metal can output stages.
Ahh , this Parasound uses my favorite 2SC3519/2SA1386 (Sanken?). All my amps use these , 70C is what 2 of them have.
You could replace with a self resetting T switch.
Nice amp , simple complimentary (Leach DIY) stage with the JC fet's.....
OS
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Those are just thermal switches, they are in series with the speaker relay drive circuit. When the heatsink gets hot enough the switch will open de-energizing the speaker relay and removing the load that's causing the heat. They will/should reset when the temp. comes down. It's all on the schematic, at least the HCA-1000 schematic. The brown goo is just glue, all off-shore equipment is slathered with it.
Craig
Craig
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Thanks Craig! The HCA -1205 diagram doesn't say much. Is the brown stuff cause for concern? Should I replace them while I am redoing the Caps? I am trying to get the amp running and almost all of the Thermal Switches have brown stuff. I just don't know if that is a failure, or normal adhesive or something. Do you know the temperature cut off if I were to need to replace them? I see there are 2 types of switches. Always on and always off. Your post seems to indicate they would be the on type if I need to replace.
They should be Normally Closed at room temp and Open at whatever temp they're designed for. Just measure the continuity, should be a short, if OK just leave them. I wouldn't worry about the glue, like I said most off-shore manufactured electronics have it especially large circuit board mounted electrolytic capacitors. In your pictures the clips that hold them in contact with the heatsink don't look very tight. Maybe bent the clips a bit so the switches are in good contact with the heatsink.
I've studied the HCA-1205A schematic and I see no thermal switches, not sure where they are in the circuit. Where do the blue wires go?
I've studied the HCA-1205A schematic and I see no thermal switches, not sure where they are in the circuit. Where do the blue wires go?
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I think it's a 95°C temperature control switch.
For example, the T70AR6U2 is a 70°C temperature control switch.
T70AR6U2
https://www.diyaudio.com/community/...in-marsh-a200s-amplifier.417402/#post-7786059