开云体育

Hello Tek experts:

Recently I bought a R7844 mainframe. The screen had some dead spots but overall can display focused traces. I transported it in a suitcase through an international flight.
It arrived with a bent handle, even worse was that now the displayed images are all skewed, as shown in the pictures.
I pulled out the tube for a visual check, it appeared O.K. except a tiny glass chip got lose inside the tube. Re-install the tube, the distortion remain the same.
Is there any hope that the image distortion is due to electrical problems, e.g. circuit board, electrical components got loose during the transit?

I also have another R7844, with broken power supply and no horizontal scan on one trace. Is it possible to transplant the tube from the one with broken power supply to another one with damaged CRT?

Maybe transplant all circuit boards on the CRT side with the tube can save a lot work of realignment?

These two R7844's are slightly different: One with dedicated vertical system so beam one is for left vertical amp, beam two is for the right vertical channel. Another one is the standard version with switches to select which beam to display which vertical channels. The dedicated system also got an extra board of enhanced display speed.

Any suggestion on which mainframe to build a working R7844?

Thank you in advanced!

yjwu

That glass chip probably hit and made a dent in the expansion mesh dome at the front of the electron gun, so it's not fixable, although still sort of usable - and a good conversation piece. It should be much easier to swap CRTs than all the rest of the guts between units.

?

Ed

Hell Ed:

Thank you for your quick response. The CRT now maybe a museum piece.

I thought of transplanting all the boards surrounding CRT, along with the tube, could possible save the work of re-adjusting all the CRT related parameters. That sum up to almost all boards on the CRT side of the mainframe?

Any suggestion on the merit of dedicated vertical system v.s. standard one? Maybe less junction, but less flexible?

Thank you again!

yjwu

It certainly looks similar to the other examples I have seen of expansion mesh
damage which fits with both the piece rattling around inside the CRT and the
damage to the handle.

I think the only CRT related parameter I would worry about is the vertical
transient response because it is the most difficult to calibrate. Transplanting
the vertical amplifiers would help with that. The other calibrations are much
easier.

I would prefer the standard system versus the dedicated system because then 4
traces could be displayed without readout interference.