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Chuckster_in_Jax
February 5th, 2009, 03:41 PM
I received a Televideo TS802 "All-in-One" computer today. I always inspect computers before I turn them on to make sure there are no broken parts or screws have come loose and could short out a circuit board. Everything looked OK so I turned it on. Light on the floppy drive came on like it was trying to boot, but there was nothing on the display. The neck of the CRT was glowing which was a good sign, but the high voltage section was down. If the high voltage section is operating you can tell by the static charge on the front of the screen.
Upon further inspection I found a Motorola K1114A 23.814MHZ crystal oscillator in the bottom of the case with the pins broken off. Turns out it is the oscillator for the terminal section of the unit. Since the horizontal sync signal is derived form that oscillator, I believe this may be the reason there is no output from the flyback. Anyway, the display is completely dead without it.

I am not having much luck in finding one of these oscillators on the net. Does anyone know of a source for these parts?

Chuck(G)
February 5th, 2009, 05:10 PM
Try these guys (http://www.io.com/~oe/). They claim to have your frequency in stock.

Chuckster_in_Jax
February 5th, 2009, 05:49 PM
Try these guys (http://www.io.com/~oe/). They claim to have your frequency in stock.

Sent them an e:mail. See what they have. Thanks!

Chuckster_in_Jax
February 5th, 2009, 06:18 PM
I have found a supplier that has an oscillator that runs @ 24.174MHZ.
If I replaced the stock 23.814Mhz with a 24.174Mhz, would that cause a problem? I don't know if you can only use an exact replacement or if there is a little wiggly room here.

Chuck(G)
February 5th, 2009, 06:58 PM
Well, that oscillator drives the baud rate clock input on the 6551 UART at position A56 and the TMR1 input to the Z80 CTC baud rate circuit at A25. Looks like it'll drive the baud rate clocks about 1.5% fast. You probably can get away with it.

A 24.000 XO might halve that error.

patscc
February 5th, 2009, 07:13 PM
Digikey has a 23.587 Mhz.
Use the selector here:
http://www.digikey.com/scripts/dksearch/dksus.dll?Cat=852334&keywords=crystal
patscc

Chuckster_in_Jax
February 5th, 2009, 07:44 PM
Thanks guys. That answers my questions. I'll order tomorrow!

Chuckster_in_Jax
February 25th, 2009, 02:46 PM
Replaced the broken 23.814MHZ oscillator with a 24.000 Mhz. The computer is alive now and prompting for a boot diskette.
Yeah!