6235 can someone explain how the transfer voltage works

**fishleg** · 09-24-2021

Hi,

I've got a machine with very faint copies. I can't understand the path of the secondary transfer voltage. There's 2 springs one is the earth for the discharge comb but the main voltage going to the transfer roller makes contact with plastic. How does the voltage go through that unless it is somehow conductive?

I wish I took pictures to be honest at first I thought nah something has fallen off as I was expecting some kind of spring touching the transfer roller shaft but on these it's all plastic.

Hard to explain but the bias spring with door shut connects to black plastic which is then connected to the transfer roller shaft. I'm fairly confident it's the hv board as I swapped the door with another machine to check and the image was perfectly fine on the belt.

Screenshot_20210924-192528_Samsung capture~2.jpg

**blackcat4866** · 09-25-2021

I used to have a photo .... sorry, I can't find it. There was a Gemini and a Mebius, in which the customer had slammed the rear cover hard enough to shatter the secondary transfer bushing that you have indicated.

The plastic IS semi-conductive to make the secondary transfer connection. I personally, was worried that the epoxy that I used would act like an insulator, blocking the electrical connection. To my surprise, the epoxy was conductive enough to second transfer, and produced a nice image. And the bushing lasted the two weeks it took for the part to arrive. The one-piece intact bushing ohmed out at 1600 ohms. The epoxied part ohmed out at 5K ohms, but worked fine.

Does that help? =^..^=

**fishleg** · 09-25-2021

Originally Posted by blackcat4866

I used to have a photo .... sorry, I can't find it. There was a Gemini and a Mebius, in which the customer had slammed the rear cover hard enough to shatter the secondary transfer bushing that you have indicated.

The plastic IS semi-conductive to make the secondary transfer connection. I personally, was worried that the epoxy that I used would act like an insulator, blocking the electrical connection. To my surprise, the epoxy was conductive enough to second transfer, and produced a nice image. And the bushing lasted the two weeks it took for the part to arrive. The one-piece intact bushing ohmed out at 1600 ohms. The epoxied part ohmed out at 5K ohms, but worked fine.

Does that help? =^..^=

It does thank you. It really had me stumped I was thinking there has to be some thing missing. Never seen a machine that uses conductive plastic to do that. Kinda cool but very confusing when trying to trace it. I was using continuity test on my meter but I couldn't get it to bell didn't think to use resistance.

**blackcat4866** · 09-25-2021

Originally Posted by fishleg

It does thank you. It really had me stumped I was thinking there has to be some thing missing. Never seen a machine that uses conductive plastic to do that. Kinda cool but very confusing when trying to trace it. I was using continuity test on my meter but I couldn't get it to bell didn't think to use resistance.

I don't know about your meter, but on continuity my meter is only good up to 100ohms. =^..^=

**fishleg** · 09-25-2021

Originally Posted by blackcat4866

I don't know about your meter, but on continuity my meter is only good up to 100ohms. =^..^=

Thanks again still learning. Sad but you know what I'll be doing when I go back lol curious what ohms it is..

**fishleg** · 10-12-2021

Originally Posted by blackcat4866

I don't know about your meter, but on continuity my meter is only good up to 100ohms. =^..^=

I went back with a high voltage and it turns out it had a dead short to ground on the spring. I placed a bit of insulation tape behind the plastic the spring sits on behind high voltage and fired back up with old board copies back to normal. It must of had a hairline crack in the plastic.

Thanks again though would never have guessed the plastic was conductive I thought it was some kind of shield and I was missing some metal...