Hitachi RPTV convergence issue

[zacheriaj]

Hello, I am fixing a Hitachi rear projection and here is the issue. Convergence was bad so I pulled the board, replaced the STK392-110 ics with STK394-160. Checked all resistors and they are fine, no pico fuses to be blown. Put the board back in, power supply turned on fine, two faint clicks and the screen doesn't turn on. pulled the PSU and the Convergence board and find that E905 on the PSU is open and GF01 and GF02 on the convergence board are open. One cause that i'm wondering about is if the outputs on the flyback transformer matter or not. Those are the only three cables I forgot to mark like a rookie Obviously the middle CRT goes to the middle. With the PSU and Convergence board out, can I replace fuses and force on the PSU to test and see if they blow again? Double checked soldering and there are no bridges or bad connections.

This is why I prefer to work on LED, LCD, and Plasma

[tom66]

Re: Hitachi RPTV convergence issue

Yes the order of the connectors on the flyback really do matter!

One is the EHT voltage (20~30kVDC), one is the SCREEN voltage (200~500VDC) and one is the FOCUS voltage (3~5kVDC)

Getting them in the wrong order could destroy the tube(s)

[zacheriaj]

Re: Hitachi RPTV convergence issue

So its possible that replacing the fuses and wiring those correctly will be ok then. If I didn't damage anything. The pico fuse that's blown is marked 3000 and the two cartridge fuses only have the letter T on them so not sure of the current ratings..

[tom66]

Re: Hitachi RPTV convergence issue

Well, I don't know if damage has been done to the CRTs...

[zacheriaj]

Re: Hitachi RPTV convergence issue

Say that the fuses caught it in time, what's the best way to determine which goes where? And how would I find the values of the fuses

[R_J]

Re: Hitachi RPTV convergence issue

The three high voltage outputs on the flyback are the same,It does'nt matter which crt's hv lead goes into which connector on the flyback. GF01and GF02 are spark gaps they will check open.
The pico fuses are marked in ma. 3000 = 3amp; 4000 = 4amp
On some chassis's e905 fuse is for the +220v to the crt boards
Best I can do without a model or chassis number.

[zacheriaj]

Re: Hitachi RPTV convergence issue

Interesting because GF03 shows closed. When I plug it in, PSU starts fine just no power to the convergence board it seems. And I was mistaken its not e905 its e907 that's open. Any ideas?