View Full Version : 2" Miniature TV/Radio Strange Problem


compucat
08-17-2013, 06:12 PM
I purchased a Broksonic 2 inch TV and AM/FM shortwave radio. This is that set that was sold under many different brand names including Realistic. I have a Realistic branded version but I have always wanted the one with shortwave band. I found one in practically unused condition with all accessories. The original owner bought it to use during storms and it was only used twice. the trouble I am having is with the radio. At first, the radio would work intermitently. Resoldering the function selector switch sorted that out when Deoxit did not help. While the radio works consistently now on AM and shortwave, the FM band sometimes loses reception starting with the upper end of the dial and gradually moves downward. If I leave it off for a day it comes back and works fine. Using the TV seems to bring it on if I have the TV on for an hour or so then switch to FM it acts up. It does not seem to be a bad connection as far as I can tell. I am wondering if an electrolytic cap can cause this as a result of the set sitting unused for almost the past 29 years. When I had the set opened up there were no electrolytics leaking or bulging. Everything inside looks factory fresh. I really want to use this as the radio is nice and the TV is functional with my agile modulator. I have never had a problem with one of these sets except a Unisonic version that would blow the internal fuse when the batteries got weak. These are generally well made little sets that sold for $200 when new 30 years ago. I would be interested in any suggestions.

jr_tech
08-17-2013, 07:11 PM
How is it being powered? Is the supply voltage dropping after the set is on for a while? This could possibly cause the local oscillator for the FM to stop oscillating at the high end of the band.

jr

Sandy G
08-17-2013, 07:14 PM
I have a couple of those little guys...Problem I have w/'em is the tuning knob & whatever its hooked to, seem to be kinda "Rubbery" & make it hard to tune in an SW station easily...They ARE Cute l'il buggers, though..

compucat
08-17-2013, 07:24 PM
I have a couple of those little guys...Problem I have w/'em is the tuning knob & whatever its hooked to, seem to be kinda "Rubbery" & make it hard to tune in an SW station easily...They ARE Cute l'il buggers, though..

That rubbery feeling is called backlash and yes there is a lot of it. Even on AM I have to rock the knob back and forth to fine tune. I can see the main design objective for these sets was miniaturization hence the very small knobs and no bandspread through reduction gears or anything like that. I absolutely love the 2" B&W picture on these, so clear and when you turn it off, the picture collapses to a dot like the sets of old.

Here is a picture of it from the auction listing. This set is cosmetically mint including the fitted carry case and yes i have the snap on front cover and carry strap.

Sandy G
08-17-2013, 07:38 PM
Well, R-390As they ain't....But they ARE good for what they are....And my examples aren't likely going away anytime soon... I've had a BUNCH of 'em....Some kid would come by here & see one of 'em, fall in love, & I'd end up just givin' it away..I'm bad to do that...A Kid grinning at me can melt/soften the cold, hard thing that semi-passes for a heart..

compucat
08-17-2013, 07:54 PM
How is it being powered? Is the supply voltage dropping after the set is on for a while? This could possibly cause the local oscillator for the FM to stop oscillating at the high end of the band.

jr

I have been powering it from new alkaline batteries and from fully charged NiMH rechargeable batteries. Also, I have run it briefly from the mains adaptor. So far choice of power source has had no affect on performance.

Eric H
08-17-2013, 08:08 PM
I have one of those too.

I'm guessing it uses a mechanical tuning capacitor, not an electronic type, if that's true then it might be possible that the plates are shorting out on the FM section, the fact that it does it worse at one end would support that theory.
The mechanical tuners in stuff like this are so tiny I doubt it would be something that's repairable.

compucat
08-17-2013, 08:57 PM
I have one of those too.

I'm guessing it uses a mechanical tuning capacitor, not an electronic type, if that's true then it might be possible that the plates are shorting out on the FM section, the fact that it does it worse at one end would support that theory.
The mechanical tuners in stuff like this are so tiny I doubt it would be something that's repairable.

It is not the tuner, I know how that can happen though as I have seen it on other radios. The radio tuner in this set is a typical transistor radio size tuner and could be replaced easily if needed. Despite the small size, this set does not seem to use any surface mount parts. It is actually quite serviceable.

centralradio
04-09-2014, 07:26 PM
I have one of those made by Unisonic made back in the early 1980's.
Radio shack had the same set under their name too.
I got the Unisonic XL-990 Schematic somewhere here.As I remember the TV tuner was Varactor tuned and the set was multiple country function switch on the side..

Photo not my set.Web photo.

Sandy G
04-09-2014, 07:40 PM
That rubbery feeling is called backlash and yes there is a lot of it. Even on AM I have to rock the knob back and forth to fine tune. I can see the main design objective for these sets was miniaturization hence the very small knobs and no bandspread through reduction gears or anything like that. I absolutely love the 2" B&W picture on these, so clear and when you turn it off, the picture collapses to a dot like the sets of old.

Here is a picture of it from the auction listing. This set is cosmetically mint including the fitted carry case and yes i have the snap on front cover and carry strap.

Part of it, too, in MY case, especially, could be trying to use "Island-Sized ARTHRITIC paws" on such a teeny-tiny tuning knob.... (grin)

compucat
04-12-2014, 11:27 AM
I have been using this set on and off for the past several months and the problem I was having of the upper FM band fading out has gone away. I am thinking it was a capacitor that has reformed from use. This set was NOS until I bought it last year. That means it has been sitting unused since the 1980s. I had two identical transistor radios from the 1960s I bought NOS in the early 2000s and both did not work due to dried out electrolytics. I recapped one and it works like new. The other one is still waiting. This little TV works great with my agile modulator broadcasting on channel 5 tuned to MeTV. It is fun to watch period shows on it right over the air. The radio is quite decent too. My wife says it looks like a car radio with the low profile form factor. I have another one of these in the Realistic branded AM/FM version with no multi standard reception feature.