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Power supply

A

abruno17

Experienced Member
Joined
Mar 10, 2020
Messages
188
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4104 Longworth Loop Kissimme, FL 34744
So My Model 4 would turn on but a bunch a garbage on the screen. I tried removing a blown capacitor labeled c32 on the board but it caused the power to go off in my room and I saw a spark fly. What is wrong? Is my power supply faulty. If so is there someone I can send the power supply to and can they repair it out of the kindness of their heart as I have very little money right now?
 
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abruno17 said:
If anyone can suggest a way to repair it myself please let me know.
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So C32 is a RIFA. You said you tried to 'remove the blown capacitor'. Did you leave it out, did you replace it with something else? Maybe some more detail on what you did with C32? There are a lot of paper caps in that type of power supply and I'm not sure which ones you can leave out and which ones you should replace. I would suggest you replace it and any of that style capacitors in the power supply.
 
I've never tried. Since that power supply has a number of paper caps, i'm not sure myself. This is my power supply after I replaced all the paper caps in it. I would be concerned about the whole sparks thing. Did you check the Fuse?

mediuml trs-80 ps.jpg

Also, did you make sure you plugged all the wires back in?
 
If your Supply is the Tandy type make sure you turn it over and check of the Pins that are soldered to the PCB.
Those Tandy supplies have a bad problem of the solder breaking loose from around the Pins. Check each pin
with a magnifying glass, and if you see any kind of a ring around any pin, re-solder each of the Pins.

If you have properly removed C32 on a Tandy supply you should be able to run it without C32.

Sounds like you could have a loose Pin or two. Check it.

I just checked a Tandy supply and C32 is a RIFA .22uF 250 VAC cap. I'd buy a fresh one and replace it.

Larry
 
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Q:
abruno17 said:
So My Model 4 would turn on but a bunch a garbage on the screen.
Click to expand...
A: not related to PSU, likely issue a bad ram.

Q:
abruno17 said:
I tried removing a blown capacitor labeled c32 on the board but it caused the power to go off in my room and I saw a spark fly. What is wrong?
Click to expand...
A: before I can answer, first a few question;
Q1:was the computer on or plugged into the power when you expertly reached inside and attempted to clip the RIFA out of the PSU ?
Q2: a spark and lights going out tells me the power was still connected (in case you said no in Q1) because if it was not connected to any source of power it would not of affected your house (trigger a breaker in house fuse box)
A1: is there possibly damaged components on your main board by fiddling with a pair of pliers into a hot PSU, yes of course there could be, but the real question is who is going to diagnose that?

Q3:
abruno17 said:
I removed a piece of metal from the solder pads of c32 is this what was causing the short or is the capacitor I removed necessary for operation?
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A: are you stating you removed the solder pads from the PSU board or are you asking? normally to remove the RIFA without planning to replace it, one simply cuts the 2 legs of the RIFA.

Q4:
abruno17 said:
When I only plug in the ac line I hear clicking
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A: normal they need a load to operated normally, plug in the floppy drives into it, then use a multimeter and test the power output.

(and if you have no idea what this means stop, find someone that does in your area before you make things worst)
 
Patrick Bureau said:
A: before I can answer, first a few question;
Q1:was the computer on or plugged into the power when you expertly reached inside and attempted to clip the RIFA out of the PSU ?
Q2: a spark and lights going out tells me the power was still connected (in case you said no in Q1) because if it was not connected to any source of power it would not of affected your house (trigger a breaker in house fuse box)
A1: is there possibly damaged components on your main board by fiddling with a pair of pliers into a hot PSU, yes of course there could be, but the real question is who is going to diagnose that?
Click to expand...

I -hope- he did this with it turned off and unplugged, and when he plugged it back in and turned it on it did this... Hopefully no-one is working inside a hot system, on a power supply, that also contains a CRT.

But yeah, the reason I asked if everything was connected back up is that this sounds like an issue (the clicking) when drives/crt cables are not re-attached.
 
Relax I completely removed the power supply when I removed the capacitor. I also removed the C33 capacitor. If anyone has the right capacitors or a new power supply and ram chips and willing to mail them to me please let me know. I'm kind in a bind in terms of money.
 
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Here is what happened. I removed the power supply and completely disconnected it. Then I removed the capacitors. The when I plugged it in the power went off in my room. This is what happened. Every time I try rehhoking it up it rips the breaker and I don't know why. Could a loose soldering joint be causing the circuit breaker to trip?
 
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abruno17 said:
View attachment 60296View attachment 60297
Here is the power supply I noticed on the back on some of the solder joints there are brown patches is this corrosion or burn marks?
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According to this c33 and c32 are lien filters (rifas) I know you can remove C32 (big one) without an issue not sure about c33, but possibly.
AcroRd32_hmERZDry2F.png

Now that said, plugging it in and getting a power outage in the room, indicates a short (power is grounding somewhere) in the circuit.
your going to need to test the circuits there is no way around it at this point to find the short.

as for the "marks on the backside" see image below hard to tell from such a small image but it brings me to a question, if you examine the mounting plate on the disk drive bracket do you see and "spot marks" on it?
msedge_OBKMSKgSS6.png
 
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