DIY fixes for the Zenith 880/881X Front projector

1. RGB mode for 50Hz and 60Hz

2. On-screen patterning problems (as highlighted in the Stereophile SGHT review)

1. RGB fix

The following information is to be used at the owner's risk and no damage can be the responsibility of myself.

Although the 881 has the facility for an RGB input, and according to the manual at either a 50 or 60 Hz frame frequency it does not work on early versions. There are two fixes required to use the RGB modes correctly. Firstly, on the very early models the input PCB (S-video, composite, etc.) was incorrect and can be identified by the extra wires being soldered to the read of the 9 pin D RGB input socket. The later board has the socket corrected and these wires are not required.

I have not been able to use RGB on the very early board, I think it needs separate horizontal and vertical sync signals rather than composite sync as the later boards. If this assumption is correct you could still use the sync separator I designed but utilise the pin3 vertical sync output. I didn't bother investigating this as I didn't know anyone other than myself who wanted to use the RGB input anyway (mine being a later board), feel free to try it if you want to.

The next problem is than the EPROM's in the earlier models (cannot say which) don't lock to 50 Hz on RGB no mater what you do. This is correctable by changing to a newer EPROM which you can now get from Zenith (after a lot of complaining). The new EPROM allows either a 50 or 60 Hz lock. Unfortunately, the projector needs to be setup for one frequency or the other in the service menu. To access is it is necessary to enter the 9876 factory menu and set item 32 to either 2,3, or 5 for 50 Hz mode or 0, 1 or 4 for 60 Hz mode. This isn't a problem if you are running a PAL only digibox into this input, but if you want to use a multi region DVD player and switch between R1 and R2 discs it's a real pain and cannot be changed.

Along with changing the 9876 factory menu it is also necessary to enter the 1234 factory menu and copy all the values from memory locations 210 to 230 inclusively to memory locations 232 to 252. These are vertical and EW coefficient data values for 50Hz mode.

Set item 279 to either 305 (for 50 Hz) or 255 (for 60 Hz). Then you can watch via the RGB socket, and I assure you this does fix the problem.

Zenith did produce a version which also fixed it, but the blacking control for the lower edge of the screen didn't work, so check it.

Good Luck, it took ages for my to get this sorted.

2. On-screen patterning problems

This must be the worst thing about this projector. Zenith ignore it, denying anyone can see it. Nobody else seems to complain about it, not in the newsgroups, etc. The only place ever to mention it was SGHT (so thanks to them !)

I eventually, more or less removed this problem (it took a year of emails, phone calls and faxes !)

The problem can be removed totally when watching any NTSC video (anamorphic or full screen). On PAL software some can still creep in from time to time but it's acceptable on a projector of this price.

To fix the problem it is necessary to remove the power supply and therefore this should not be tackled by an unskilled person.

Remove the projector lid, unscrew the two bolts attached to the two sides of the power supply PCB (at the back on the opposite side to the RGB input board). Then either remove the side fan, or use a long socket to remove a bolt from either side of the board also.

Remove the plug in connectors from the top of the PCB and the one on the side (can be seen easier from the side). Finally remove the HT lead from the connecting block at the front near the guns and feed it back through the case. Then gently pull the PCB upwards and it should be lifted clear.

Next is the hard part. The metal shield box, around the output transformer causes the problems. It's folded from a flat sheet and doesn't create a sufficient earth connection. To correct it, it is necessary to carefully de-solder and remove it, then solder two or three points on each folded metal seam. I have a picture of the case but it's quite obvious when you remove it from the PCB.

Once soldered, carefully re-solder it onto the PCB (take care of solder spits) and then fix it back into the case.

That's it. You can now enjoy the much improved picture and not become stressed by that annoying wavy line that use to ripple across otherwise good pictures from time to time.

Runco fix for this problem

I also tried to ask Runco about this problem, they weren't interested at all, but eventually I found a helpful chap on the net with the Runco 770 (the Zenith re-badged) who also wanted to fix the problem. Runco had 'fixed' his and this was their fix. I tried this before finally fixing it correctly using the previous technique, it did improve matters slightly, but it's far from perfect. Use it it you wish.

The following is taken directly from the e-mail sent from K.C.at iwannitall@yahoo.com who gave me the Runco fix.

• My projector is mounted on the ceiling, so this information was collected while I was looking up at it.
• Facing the rear of the projector, there's are 15 pins protruding from the board near the top. These pins are located at the upper right portion of the board.
• Counting from the last pin farthest to the right, there is a wire soldered to the 5th pin. (the 11th pin if counting from the left.
• Look to the left of these 15 pins for "C2903".
• Immediately to the left of and a little lower than "C2903" is "C2902".
• The other end of the wire described in "6." above is soldered to the two points immediately below "C2902". This end of the wire has the insulation stripped far enough back to allow the connection between the two points. (For reference, immediately below "C2902" is "W44" and to the right of this label is, "R2905" and "R2907".)

Thanks to him for that. I hope this helps, it certainly made Runco look poor when it comes to after sales care !