Xr 600B repair help

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Deenahrae
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Joined: Tue May 10, 2022 6:25 pm

Xr 600B repair help

Post by Deenahrae » Tue May 10, 2022 6:58 pm

Hi guys I’m Deenah and new here. I just got a xr600B not working and need some guidance on how to approach this repair. I’m pretty limited on my electronics repair but do have a good understanding.

So this unit I got is non functional. There are tell tail signs that this was liquid damaged, among the other oddities.
When I got it the fuse cap was missing, ground prong was pulled out of the power cord, and quick glance inside it was filthy with what looks like someone’s spilled beverage on the transistor/s. Not a lot but probably enough to kill it.
I cleaned it up a bit and did a visual inspection of the board, nothing looks burnt, caps don’t seem to have any leakage or bulging.
I replaced the fuse and holder in attempt to get some life out of it. Now before I get yelled at, I know I should have had a variac or something to slowly bring it up but I don’t.
I gave it power for a split second and I got power light and also compression light lit solid. The transformer was kinda loud however this thing is 42 years old.
I don’t want to power it up again because I can clearly see the syrup from someone’s mix drink on the transistors.
There is also a little on the side of the large caps.
I checked a few diodes and they were good, and I do have some power.
I read on here that someone else recapped theres and put in new transistors.
So where should I start with this ? I got it because when I was 15 I had a band and we had one of these in rehearsal. It’s a nostalgic thing for me.

Thanks

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dak
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Re: Xr 600B repair help

Post by dak » Thu May 12, 2022 5:35 am

When I got it the fuse cap was missing, ground prong was pulled out of the power cord, and quick glance inside it was filthy with what looks like someone’s spilled beverage on the transistor/s. Not a lot but probably enough to kill it.
Ok, that sounds like a smoking gun left by the previous owner. Pulling the ground prong could be a measure against a GFCI triggering due to bad power connections; missing fuse cap can be a message of "don't even try" to scavengers. Maybe this was just used with an isolation transformer. Loud transformer noise would be indicative of a transformer problem if it actually is transformer noise rather than induced hum (transformer noise will be 120Hz, induced hum will be 60Hz). Or bad power capacitors (also 120Hz) or a blown rectifier diode (120Hz, usually very hard on the survival of power capacitors and further components).

Either way, this should not be tested at all without the ground connection being verified to be fully operative.
I don’t want to power it up again because I can clearly see the syrup from someone’s mix drink on the transistors.
You need to get a "mix drink" inside first. Without photographs, my first guess would be that rather some capacitor spilt its drink. That would also match excessive hum.

Bartman
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Re: Xr 600B repair help

Post by Bartman » Fri May 13, 2022 10:33 am

Deenahrae wrote:
Tue May 10, 2022 6:58 pm
... I can clearly see the syrup from someone’s mix drink on the transistors.
There is also a little on the side of the large caps.
This sounds like it may be the syrup from inside the capacitors leaking out rather than someone's spilled drink on it. If it's 42 years old, those caps are surely bad by now.

LB

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