Radio Shack Pro-95 Display issue Need schem or Capacitor# for contrast

[N2BRG]

Hello Folks,
Just going through some older radios and have two like new RS Pro-95 scanners. Both have no charactors on the screen, but fully programmable. I have been through the Initialize steps 0-1 and also tried a reset. I read quite a few post here and in other forums about this issue and so far no luck with the suggestions mentioned unless I missed something. Some have mentioned due to the cheap capacitors in these radios the contrast supply cap may be bad, but no one has mentioned the capacitor part pacement on the board. I hate to throw these out or scrap for parts since they both are working minus the display. They do make good WX recievers though...
I am probably beating a dead horse here, but does anyone have a schematic or any info on what capacitor fails for the contrast display supply voltage?
Thanks.,

 

[Enforcer52]

Found this site that lists schematic/service manual but costs $17

RADIO SHACK PRO95

RADIO SHACK PRO95 Service Manual | Download the High Quality Digitized PDF, or order a High Quality Paperback Manual, Tech Sheet or Supplement.

www.servicemanuals.net

Also found a thread on RR that says to try to initialize the scanner. That worked for some people, but didn't see instructions on how to do that.

PRO-95: Dead LCD Screen

Hey guys. I recently was replacing the batterys on my PRO-95. I took out the old ones, installed the new ones, put the battery cover back on, and whattya know, it stopped working. I thought it might have been a battery problem but after calling a friend, we both determined it was a dead screen...

forums.radioreference.com

 

[tvengr]

If you have a scope, look on both sides of each electrolytic. Generally, you should see the same thing if the cap is doing its job.

 

[N2BRG]

Thanks for the quick replies, I will look into the manual purchase. These two scanners look like they just came out of the box. Hate to dump them or scrap them out. As for scoping the cap, Just need to find which cap it is. If I had specs on the display itself that could give me an idea which way to go. I'll pull the scope out anyway and see if there is any information at least getting to the screen. I may also be able to find which trace is the contrast too.

I am also plaing around withe the PRO 2035 that was packed along with the two handhelds. The 2035 is still working fine even with all the mods I have done to it. 10.7 out, Disc out built in down converter to HF and a couple other mods.
Just remembering the good ole days when you could actually hear the locals before the encryption.

 

[pro92b]

Three things to try:

From the owner's manual page 53:
Changing the Display Contrast
1. Press MANUAL.
2. Press FUNC then 9. Use Up/Down keys to set contrast appears.
3. Press 8 or 9 to select the contrast.
4. Press ENTER to set the display contrast.

On page 83 there is a procedure for resetting the scanner. If that fails then how to do a full initialization is described.

The PRO-95 owner's and service manuals are at mods.dk -> Instruction, users and service manuals for Radio_shack.
Grab the PRO-93 manuals too as the PRO-95 service manual is essentially an addendum to the PRO-93 service manual.

I don't expect a capacitor will have anything to do with the problem. Connector CN203 may need to be unplugged and reinserted several times to wipe the contacts.

 

[tvengr]

Even if you don't know which caps are in the circuit, if you find one with signal on one side and nothing on the other, there is a good chance the cap is open. The connector is another good possibility. I would check that first.

 

[gmclam]

If memory serves me correctly, the physical display is connected to the PCB with a fragile ribbon cable. The receiving connector has a "clasp" to hold it in place. If the cable is not in there ideally, that could be the issue. You'd want to unlatch the clasp, pull out the cable, and re-seat it. If it's not seated at all, therefore exposed to air, it could become tarnished. I've been successful in cleaning that with a pencil eraser. YMMV.

 

[dave3825]

If the cap is still installed on the board in the circuit, can it be scoped or does one need an ESM meter?

 

[N2BRG]

Interesting... I have tried the contrast earlier before posting and it did not work. This time around one of the radios worked, but it is not good though, it shows boken up charactors. I'll get in there and reseat the cable, but that looks like more than a reseat. If it is one of those old rubber contact type displays, that will have to be carefully be cleaned. This will be the first time either will be opened. Gee... Wonder if it is still under waranty. Just joking
The second one no go for a display even messing with the contrast. The semi working one will give me a starting point for when I pull the scope out and compair the two. Maybe I can get one working well out of the two
Thanks all for the help.

 

[cherubim]

I have a GRE PSR-295 (similar in design to the PRO-95) and its display went blank completely on power up after storing it for a few years. I tried all the suggestions (checking caps and ribbon cable to display, adjusting contrast, etc) but nothing worked. I just leave it parked on an aeronautical frequency and not worry about it.

I also had a PRO-99 go the same way which I longer use as without an active display it's a bit harder to operate. That scanner was also left unused for a long while before the display problem manifested itself. One shouldn't store any scanners for a long period of time irrespective of whether they new or used as gremlins inevitably show up.

 

[kd4bas]

I too have this issue but with a Pro-96. I have pushed the contrast up as high as it will go and its barely readable at any angle. If you figure this out, please let me know .

 

[kruser]

As @pro92b mentioned in his earlier post, disconnect and reconnect the ribbon cable that connects to the actual LCD display.
I've fixed a bunch of the Pro 93, 95 and 96 models with the same exact problem.
Reconnecting the LCD ribbon cable always fixed the display problems when it appeared to be a contrast setting problem.

The ribbon cables used for the LCD modules are often pretty fragile ribbon cables so I'm not sure if one could try to clean the contacts without damage or tearing the cable. Don't even try to clean the cables socket. I doubt I'd even trust spraying it with one of the DeoxIT contact cleaning sprays but that could help as long as the DeoxIT is the type that won't damage any plastics in the socket or cable itself.
Maybe an alcohol wipe may work to clean the cable some so the repair lasts longer?
I still have an Pro-96 to this day that needs to have its ribbon cable reconnected probably every two months or so. Eventually I'll probably wear out that radio's ribbon cable connector. Maybe I'll actually try to clean that radio's connectors and see if I can make the repair last much longer.