Dead Fender Stage 185 Amp

[benbeej]

I would appreciate any help in troubleshooting a dead SS Fender Stage 185 ampflifier. Fuse was checked out okay but it won't power up.

[Mark Black]

Near where the power hooks up to the PCB look for a broken lead or cracked solder at the inrush limiter (larg-ish, usually black but sometimes red, disc-shaped with two leads).

That's been the culprit in just about all of those I have seen with that symptom.

Good luck!

[benbeej]

Mark - Thanks so much for responding. I will check it out and post an update.

Ben

[benbeej]

Mark -
Again, thanks for helping. I was not able to locate the disc-shape inrush limiter you are referring to. I am not an electronic expert, I know a little bit and still trying to learn. Do you have a schematic that you can share with for this amp? Can you pinpoint the problem area in the schematics?
- Ben

[Mark Black]

Hi Ben -

Well - I don't have a schematic for those, although I suspect the one for the Stage-100/160 available on the Fender site will be close enough for some initial diagnostics in the power section.

As to the inrush limiter - I am going strictly by memory and it's been years since I was in one of those amps. Should be fairly close to and in series with the fuse.

If you haven't already done so this might be the time to go ahead and remove the PC board so you can get a look at the solder side. The power portion of things should be fairly easy to visually trace from the AC cord connections right through to the transformer and beyond. Look for any spot where a component lead doesn't have a nice fillet of solder around it or has an actual "ring crack" in the solder. This would also be a good time to preemptively retouch solders at all the pots, switches, large and/or heat-producing components, and anything else that is mounted to the chassis & also soldered to the PCB.

Depending on the history of the amp and whether someone else has had it apart before you the inrush limiter might actually be completely gone. See if there are any spots where there are component leads sticking through on the solder side with no corresponding component above.

You might want to check the fuse with a meter as well (if not already done) since they can be bad without looking it. Checking continuity across the power switch (power unplugged of course) is always a good idea - they don't go bad too often but it sometimes happens. Every so often you run across a bad AC cord too.

Taking some time, tracing circuit paths, and using logic & reasoning should lead you to the trouble spot eventually.

[Enzo]

On the right end of the main board, there are a bunch of push-on connector popints for the AC wiring, and also the main fuse. The inrush limiter is the thing near them in the corner sitting at an angle, SHould say TH1 next to it

[benbeej]

Hi Enzo and Mark,

Thanks for your help. I was out of town on vacation and just now getting back to reality, thus for the late response. I found the location where the inrush limiter was with TH1 label next to it and I could tell that it has been removed. There appeared to be remnant of 2 lugs where the inrush limiter was. I checked the 2 protruding metal for continuity and it is open. What can I use to replace the missing inrush limiter with?

Thanks again guys!

Ben

[Enzo]

Another one from your Fender dealer. YOu sure the thing itself is not inder the board somewhere? CHances are it broke off from vibration and fell underneath. If there are leads left on it, you might remount it.

You could replace it with a piece of wire, but you would likely have nuisance fuse blows now and then when you turn it on. Once the amp is on a few moments, it heats up and turns into essentially a piece of wire anyway.

[benbeej]

Is there an out-of-shelf replacement part aside from getting it from Fender to avoid having to wait for delays? Do you happen to know the values of the inrush current limiter? Thanks again! -Ben

[Enzo]

I have no idea, I get mine from Fender. It has a part number with no explanation, that's all I know about them. They start out with some value - how does 200 ohms sound? Then they warm up quickly and their resistance drops to very low.

[Enzo]

OK, the thing is a CL-30

Mouser sells them as stock 527-CL30 for $1.39 each.

Inrush current limiting thermistor

[benbeej]

Thanks for the quick response. I'll place the order and post an update later.

[Chillikiss]

Hi

Do you still need the schematics for the 185 Series? I have scanned copies if you would like me to send them to you.

[benbeej]

Yes, I would appreciate it very much if you can e-mail me a copy of the schematics. My e-mail address is benbeej@sbcglobal.net. Thanks.

Ben

[bgcostello]

Dead Fender Stage 185 Amp

Do you still need help with this problem? I have a Fender Pro 185 that has the same problem. The black disc inrush limiter is a 2.5 Ohm 8 Amp thermistor Fender p/n 0026411000. They can be obtained from musicpartsguru.com Phone 630-521-9170.