Re: Help with dead Commodore 1802
yes, the coil is the link from the psu stage to the tube handling.
it does not isolate the audio amplifier though.
Help with dead Commodore 1802
Collapse
X
-
Re: Help with dead Commodore 1802
Ok i gave it one final check after solderig in the STR transistor we checked and as i was afraid of it blew the now mox resistor. Those resistors give a much bigger flash than the wire wound one's. Well that is still a bit strange because i checked all component for the psu and none were shorting. Am i right in assuming that that coil i removed is the output voltage from the psu to the monitor itself. So this rules out a monitor fault and the short is isolated to the psu circuit somewhere?Leave a comment:
-
Re: Help with dead Commodore 1802
with a meter, see post #44[/QUOTE]
Thanks. It tests ok. Ive been testing everything including the STR54041 for a short and nothing tests as a short in the power supply area of the pcb except a odd iduction coils and that new metal oxcide resistor. Should i refit the STR transistor and try power it up using the light bulb as was mentioned earlier. Ive removed L805 and connected the bulb across C812. Is there anything to check before i try this and most likely blow another resistor probably.Last edited by roadrash; 06-10-2019, 01:17 PM.Leave a comment:
-
Re: Help with dead Commodore 1802
You can test the output transistor with a meter, see post #44Attached FilesLast edited by R_J; 06-10-2019, 12:01 PM.Leave a comment:
-
Re: Help with dead Commodore 1802
Leave a comment:
-
Re: Help with dead Commodore 1802
Can i use these metal oxide resistors if i blow my last wire wound one?Leave a comment:
-
Re: Help with dead Commodore 1802
It's the large one in the power supply C803Leave a comment:
-
Re: Help with dead Commodore 1802
Just to make sure what is the number of the main capacitor?Leave a comment:
-
Re: Help with dead Commodore 1802
8
On my last 3.3uf resistor here so dont reallywant to blow it up too. Ive had some mox type 3.3uf resistors turn up but can i use them?.Last edited by roadrash; 06-08-2019, 04:58 AM.Leave a comment:
-
Re: Help with dead Commodore 1802
So no short across the main capacitor?, You can also check the output transistor in the str54041 (E=pin4,C=pin3,B=pin2) however I suspect that if the str was bad it should have blown R805 (0.27Ω)Leave a comment:
-
Re: Help with dead Commodore 1802
no, it's supposed to be 0.27ohms
desolder coil L805, connect a 40w mains bulb to the pins of C812 and try it again.
then your only running the psu and the audio amp - not the rest of the circuit.
you need the light because the psu expects a load.Leave a comment:
-
Re: Help with dead Commodore 1802
All others like 4 diodes are okLeave a comment:
-
Re: Help with dead Commodore 1802
i have never seen as resistor fail without help.
a 40w lamp bulb in series with the monitor is a good idea to limit the current.
and leave the degausing coil unplugged - it's the thing that causes the bong sound - and causes a big surge.
it's around the outer edge of the front of the tube, and runs to a 2pin connector near the mains input.Leave a comment:
-
Re: Help with dead Commodore 1802
Hhahhaha yep You said it! Do you still think it a MOX because I did order a couple of these wire wound ones and a MOX one that I am still waiting to arrive. I will now do like RJ said and rty and find that short. I never expected that. there was just I small flash from the new restistor and I knew straight away and yep! its was blown. Just as well I got another.Leave a comment:
-
Re: Help with dead Commodore 1802
It blew the 3.3Ω 10 watt resistor! but not the fuse? Ok check the 4 power supply diodes, then check the resistance across the main capacitor. You must have a dead short somewhere in the primary circuit
Post a picture of that new resistor that blew openLast edited by R_J; 06-06-2019, 03:14 PM.Leave a comment:
-
Re: Help with dead Commodore 1802
I fitted a 3.3 ohm wire wound resistor and as soon as I powered it up it blew it again.Leave a comment:
-
Leave a comment:
-
Re: Help with dead Commodore 1802
The resistor is just to provide a bit of surge protection when you first turn it on. It is in the ac line, it can be made from anything, its not important.
I just used digikey to find a mfg. part number of the same type and mounting that you are replacing.
https://uk.farnell.com/international...10w/dp/1457934 £0.933Last edited by R_J; 06-05-2019, 11:06 AM.Leave a comment:
Related Topics
Collapse
-
by double_DDHi all,
As the title suggests, how can I be sure that my EC chip is really dead?
I've recently gotten into this hobby of laptop repairs, and have successfully brought back to life a couple with some easy fixes, mostly shorted caps.
Now I'm working on HP Probook 455 G8, that had some "devil" run around on 3V line, burning a bunch of stuff. Luckily I have a dead 455G7 (for spare parts) so I managed to fix it (swapped burned parts) to a point that it will charge (both on barrel jack and usb-c), but it doesn't want to turn on. There is a 3V3 on a keyboard... -
by disorderhello guys,
i need help to repair a edm-033 ps2
history : as always hdmi port and usb ports destroyed after unplugged
after change them, ps5 dead too : 1 beep, no blue light. after inspection 1.8v power was shorted, and because of dead panasonic chip. after remove it : no short anymore
so i changed it
now i have got 5v stby,, 3.3v stby, 3.3v power, 1.8v power and no short on them
but the ps5 is dead again : 1 beep, near 10 seconds with power lines and then off, no blue light ...
i don't see any projection of liquid metal on pcb.
... -
by BetonHi guys!
I searched for the term "dead short" in the forum but no specific thread came up however if I'm just blind and couldn't see the thread talking about this please forward me to that direction.
So my problem is I don't know how to find the source of a dead shorted voltage rail. Dead short = ~0 ohm resistance.
I have two VGAs (HD 4850 and HD 4870), both dead shorted to ground on the memory rail. I have the boardview file for the 4870 and the memory rail consists around ~7892346 capacitors...
I have a bench PSU and if I try to inject voltage the voltage... -
Hello everyone hope all doing well!
I have this PSU (GPS450-AA delta oem) around for like 4-5 years and I had it recapped early 2020 or 2021 with mostly UCC KY and Nichicon PW's. The bulk was and still is fine, the original Ltec's were bloated and empty. The previous issue was some major coil whine noise and at times random shutdowns when going idle. Today it started tripping the mains breaker and I think I have dead APFC mosfets (20N60C3). Right now upon checking I have the Q1 and Q3 FETs dead so far and I guess those are responsible for the PFC circuit. The only thing I care is If there...3 Photos -
Hello, today I'm working on this lovely MSI Raider GE75 gaming laptop which I bought to flip. Unfortunately, I believe the CPU is toast but I wanted a second opinion before I chucked it into my spare parts bin. I will not have most tools with me today as I'm away from my workbench but I have the basics (a good multimeter, a horrible iron, a solid screwdriver, and my trusty thermal cam). I do not have the original 230w charger, but I have a Dell 180w which was sold with the device and reportedly "worked fine for them".
Specs: I7-10750H, RTX 2060, 32GB RAM (unknown manufacturer)... - Loading...
- No more items.
Leave a comment: