Hello all,

I've acquired a JVC P100 2" portable TV/radio combo. The unit is virtually spotless, however the poor little guy has a couple of issues:

1. TV tuning range on VHF and UHF will not tune across the band, it seems stuck on a small portion of each band even though the tuning potentiometer (it uses a voltage controlled tuner) is turning from end to end with no slip.

2. The radio section works on FM but not AM.

Without a schematic I'm stuck, and the dial cord is strung throughout the unit in a merciless way, making me aprehensive to jump in unguided. It seems that symptoms along these lines are common as I've run across similar issues attempting to scour for a diagram.

Does anyone have a schematic that they could post?

Thanks,

I don't, but that TV was also sold as an Emerson, if that helps in finding a schematic. Nice little set! I've had a couple of them.

Charles

I checked the Emerson and it is a different animal. It looks similar on the outside, but inside its a different story. Who ever designed this one (likely Orion) learned a thing or two from the JVC version, as the inside is missing the insanely complex radio dial stringing and has only one shielded module (the TV tuner). I'm leaning toward a power supply regulation issue because the IF amp IC on the radio board has low supply voltage preventing the LO on the AM tuner from working.

I think the Realistic version is the same as the Emerson as well as its a dead ringer.

The Emerson one can be seen on:
http://www.taschenfernseher.de/bilder/nordmendetr101inside.jpg

I'll post some pix of the inside of the JVC version when I get a moment.

It is interesting to note that they didn't secure the tube in either unit.

There were 2 Emersons; one more like the Sanyo TPM2100 (your picture above), and the one I thought was like the JVC (round dial in speaker grille, etc). I think I even used a JVC shematic on one of those at work a long time ago, but I could be wrong. I know I've seen a third one too, and I can't remember the badge on it.

Charles

Hi ColorFixer, Hi Charles,

1) JVC P-100

I think i have the Euro version of the JVC P-100 in my paper files. Horrid to scan 3 square feet full-sized folding type.

Quick Fix tips: TV tuning is achieved by a pot run from a (usually) 33V DC line which generates a 0 to 33V tuning voltage for a bunch of Varactor diodes inside the tuner. Try finding the "tuning voltage" pin of the shielded TV tuner can, connect a DC multimeter and scan a TV Band. You should see a varying voltage there.

- use a modern VOM as the 33V line only feeds a few tens of microAmps.
- from memory, the highest end of the Band- Ch 83 needs the most voltage.

If the tuning voltage won't reach above 20-25-30V, probably some dead caps in the voltage multiplier section.

In mine, all Lytics were dead = shotgun recap.

2) Emerson VR-22 aka Orion TVR-7120
A 2" B&W screen + AM/FM mono radio

I think ORION was the OEM and it was sold under a bewildering array of private label brands all over the world, for instance: Nordmende, Brandt, Orion, Radio-Shack RealisTic PortaVision, Audiosonic, Broksonic, Emerson, Continental Edison, Nippon, ISP, TMK, etc.

Frank's Pocket TV site more/less quotes them all.

They are astoundingly reliable! i admit sheepeeshly to having a fair number of them and practically all worked A-OK after pot & band switch cleaning.

Came in many flavors (case colors, etc)
USA TV only + AM/FM radio

USA + Euro TV with Euro/UK/USA audio
LW + AM + FM radio

Euro TV + UK TV + French TV (625)
LW + AM + FM radio

Maybe some for Brazil & Argentina?

etc.

Tough, hard working little guys. CRT stay bright forever and they're darn cute.
Entirely Japan made build quality or key Japanese parts (CRTs) + assembly in Taiwan - far and above the Chinese 5" BPCs which came later.
Note that China never attacked the 2" B&W CRT market. My personal opinion is that their electron optics knowledge was far too poor to rival the Matsushita, NEC Citizen, Hitachi & Sony 2" down to viewfinder sized tubes.

Use around your house with a cheap second hand "high power" Blonder-Tongue modulator used as a TV transmitter.

Best Regards

jhalphen
Paris/France

Thanks Jerome.

I have just such a modulator with a 20dB CATV amplifier and a UHF folded dipole antenna (470-512MHz). I use it on my PC-101 (Canadian version of CT-101) all over the yard.

As soon as I unearth a schematic, I'll tear into it to and post what I find. Hopefully someone will take pity on me and reveal as to how to take the set apart without having to de-string the radio tuner.:yikes: I'm concerned that there are multiple sections in the radio's tuning capacitor that may have seized, even though the FM section's tuning works. I'll know more once I get inside and personal with it.

I figured that there is some form of voltage converter lurking inside a la Sony VTX-1000. Normally, I expect 34' odd year capacitors in a tv to be bad, just not ones that seem to hardly have been used (read cooked from heat).

I'm sure that these were ruthlessly cloned by Orion and General Shikoku. Didn't JVC make stuff for Ferguson in the UK? They did private label in Canada for a number of different department stores.

I'm of the same opinion that chinese electron gun optics were pretty primitive until the Japanese opened factories in China to build CRTs, which really didn't happen until the end of 80's. I can vouch for stuff made by Orion. I have a monitor that was made by Orion in 1984. It must have over 50,000 hours on it since it was in an arcade game up to a couple of years ago, and is still bright and sharp with plenty of emission.

Hi Colorfixer,

Tell you what, give me your Mail address by PM and i will send you the bigger than A4 service data as high-res jpg photos taken with a Panasonic Lumix camera.

For other vital sections, i.e. "take apart", etc, i will do quick scans.

Noted that you also need the AM/FM radio section. I don't think that your radio's variable cap has seized because all 4 sections, 2x AM, 2xFM are on the same shaft.

Best Regards

jhalphen
Paris/France

Thanks to jhalphen's time to scan the manual, I was able to repair the multiple faults that the set developed from three components. My results are posted here for all to enjoy.

Disassembly is somewhat challenging: You need to remove the three slide switch knobs (carefully) first. Next, remove the three front knobs, followed by all the screws accessible on the cabinet. To remove the radio board from the rest of the unit, remove the metal tab wrapped around the wires running across the top front to the tv tuning pot. Gently remove the black backdrop under the radio tuning scale, then the blue screw located beneath. There are two more blue screws: one accessible from the bottom of the unit, one on the top directly in the middle front of the unit. Gently slide the whole assembly back and tilt it to the right out of the way. It will be connected to the main board with a 4 pin molex connector which carries audio, antenna, and power to the radio. By carefully removing the tuning drum's small phillips head screw (it is locktited on), the board can be carefully removed without having to destring the tuner (not a task for the faint of heart).

The first was the inability to tune the tv on either UHF or VHF. Looking at the VT terminal on the tuner, I found that the tuning voltage varied from 0.2 to 0.5V. Tracing back, I found C503 had totally leaked, corroding the traces under the capacitor completely away. Tracing the lines back revealed that they were corroded under a connector they ran through as well, necessating removal and cleaning of the board underneath as well. Replacing the cap allowed me to move on.

Now I had tuning voltages that were closer to what I expected, I still found that the range while nearly right, wouldn't tune across the VHF band properly. The 30V supply is derrived from the flyback, and C401 had high ESR. Replacing this solved this as well as ripple on the supply that causes the vertical hold to lock out of phase.

The radio board however really made me scratch my head. The AM tuner was completely dead. I quickly determined that the LO on the AM tuner was not running. All the components relating to the AM converter checked out and the DC voltages were nearly spot on, so I was beginning to fear a bad IF coil. When I ran my moist fingers across the board near the converter transistor, I suddenly heard noise. Checking the LO while holding my finger in the right point revealed the oscillator running. After some more prodding, I discovered R823 while the right value according to the schematic, did not provide enough bias voltage for the circuit to start. Reducing this value with a substitution box revealed that the original value was almost twice what was needed to allow the oscillator to start. Replacing this with 220k made it start 100% of the time.

From what I can see of the control layout and case on that set it looks a lot like the Broksonic I just got.

http://videokarma.org/showpost.php?p=3020542&postcount=872

Hi ColorFixer,

I'm glad the info supplied helped you repair this cute little JVC and i admire your diagnostics savvy.

Being in Canada, apparently you still have some UHF TV activity, maybe university stations & low power local broadcasters.

The AM section of the JVC P-100 should be somewhat above average, i noticed it used a FET transistor in its RF stage.

Once again, congratulations! on reviving a quality electronic item from the past, they don't build them like that anymore.

to Eric H. - external appearances can be deceitful. Your Broksonic is indeed the Orion originated design sold under a dozen labels at least. Outwardly, it looks a lot like the JVC P-100 but schematics-wise it's quite a different animal. JVC really designed their model in-house from the ground-up.

Best regards

jhalphen
Paris/France

Almost all the UHF/VHF NTSC operating anywhere near large markets has been turned off as they were translators that relied on donor transmitters that were NTSC. Where I live in northwest Washington is too close to the Vancouver and Victoria BC market to allow analog. There is supposed to be a few translators around, but I'll be hard pressed to find them. The only real solution is to use a set top box and a modulator to rebroadcast. I wish we could cobble enough technology to build a board to retrofit into vintage portables to run ATSC.

Jerome,

Yes, the FET plus the slightly higher current through the converter stage makes for a really hot receiver. Its more sensitive than my Sony XDRF1HD tuner. I work near four 50kW AM flamethrowers and it just doesn't overload.

Hello Colorfixer how are you? I have a JVC P-100EUC with the same problems as yours (does not tune in VHF or UHF). The radio part is ok. I read your explanations but I don't have the schematic, only your 3 jpeg images, so it's very hard for me to get the TV fixed. Can you send me the schematic?
Grateful in advance, Pedro Araújo (I'm from Portugal and I apologize for my bad English)

Pedro
Your English is fine. Always fell free to come & post your questions & answers.

73 Zeno:smoke:
LFOD !

Hello Colorfixer how are you? I have a JVC P-100EUC with the same problems as yours (does not tune in VHF or UHF). The radio part is ok. I read your explanations but I don't have the schematic, only your 3 jpeg images, so it's very hard for me to get the TV fixed. Can you send me the schematic?
Grateful in advance, Pedro Araújo (I'm from Portugal and I apologize for my bad English)