Thread
PowerMac G3 All-in-One, iMac G3 - Same Symptoms
So today a friend of mine came in with a big and beige PowerMac. It powers on and works, but the screen and picture tend to pop and go out. Are these models prone to flyback failures like the G3 iMacs? I'm hoping I won't have to handle another fried flyback. I'm still trying to find any shorts in my G3 iMac Rev C with the same issue, though much louder and frequent pops. The iMac is already disassembled and ready to be tested, even if removing the flyback has proven difficult. Chances are its working parts will be sold off and the case repurposed into a cat bed.
I haven't had a PowerMac like this one to work on. Is it going to be a simple fix or a headache flyback problem?
I haven't had a PowerMac like this one to work on. Is it going to be a simple fix or a headache flyback problem?
the flyback is bad.
no ifs ands or buts about it. I had changed a couple out in G3 AIOs way back in the day for this exact issue. the flybacks were made by goldstar and hungwa or some shit like that. I had a cross-reference. But this was back in high school and that information is long long gone.
But its not the flyback itself, its the Focus/G2 block that is molded part of it. What happens is dirt gets in there, moisture, etc.. These pots are super high impedance so the substrate has to be manufactured accordingly, This breaks down and the high voltage arcs over into the focus/G2 parts of the electron gun on the CRT. and thats the arcing you hear.
Another problem is the high voltage itself could be a bit excessive if the hold-down capacitors in the horiz output stage go bad. A good HV probe should indicate if there is a problem in this area. the HV should never ever exceed 23KV in a CRT that small.
In rare cases on something that is ir-replaceable, older TVs the G2/Focus block was separate from the flyback, and went in-line with the HV. Sometimes if you can locate a replacement block, you can cut the leads off the flyback and wire it to the system itself.
no ifs ands or buts about it. I had changed a couple out in G3 AIOs way back in the day for this exact issue. the flybacks were made by goldstar and hungwa or some shit like that. I had a cross-reference. But this was back in high school and that information is long long gone.
But its not the flyback itself, its the Focus/G2 block that is molded part of it. What happens is dirt gets in there, moisture, etc.. These pots are super high impedance so the substrate has to be manufactured accordingly, This breaks down and the high voltage arcs over into the focus/G2 parts of the electron gun on the CRT. and thats the arcing you hear.
Another problem is the high voltage itself could be a bit excessive if the hold-down capacitors in the horiz output stage go bad. A good HV probe should indicate if there is a problem in this area. the HV should never ever exceed 23KV in a CRT that small.
In rare cases on something that is ir-replaceable, older TVs the G2/Focus block was separate from the flyback, and went in-line with the HV. Sometimes if you can locate a replacement block, you can cut the leads off the flyback and wire it to the system itself.
Guess this one may face a CRT to LCD transplant at some point in the future. It looks like it was upgraded quite a bit, so I don't want to lose that. I just don't like fidgeting with flybacks and their near by components that require more work than "replace that cap".
Mmmmm at this point in time, a machine has to be fairly special to warrant me bothering with a flyback replacement. If one were to fail on either of my iMacs for instance, I dare say at this stage I would simply just replace the whole A-board with a known good unit. If I had something rareish like a Lisa or something then obviously that would change things a little.
But yes, an LCD swap sounds like a better long term option if you arent a stickler for authenticity.
But yes, an LCD swap sounds like a better long term option if you arent a stickler for authenticity.