Perdio Portarama mk2

[matthewhouse]

Hello again,
I'm currently doing one of these little portable TVs but am having a few problems. The first is the wiring to the tuner unit. There is 2 coaxes and 3 wires going to it however one of the wires (purple) is just floating about. According to the trader sheet it should go to one of the terminals on the tuner, however there is already a wire (yellow) on this terminal. Looking at the circuit again the yellow wire should be one terminal away, which connects to the cathode of D1, however nothing is connected here. It is clear this has been changed at some point as the wire is poorly 'stuck' on. The problem is, that when the wires are fitted as per the circuit (this is looks right as the 3 wires won't all reach in any other configuration) the picture is not clear. Putting the yellow wire back where it was and grounding the purple wire gives a superb picture, and the contrast is then fully adjustable. But clearly this can't be right? Although there is a blob of solder on the tuner unit where the purple wire would reach nicely, could this have been some form of modification?

The other problem I'm having is the sound is putting ripples onto the picture, with the audio disconnected the picture is fine. I have re soldered several dry joints and the HT measures -11.6V.

[Steve_P]

Try reducing the RF power output from the 405 Converter. It may be too high. Or the sound may be too high.

There are 2 versions of tuner on these. Which one have you got. Trader Sheets 1652 and 1653 deal with them.

They also have alignment details if needed.

Cheers,

Steve P.

[matthewhouse]

Thanks for the quick reply, tried reducing the power but no help, this fault intermittently clears itself.

Looking at the 1652 sheet it appears to use the alternative tuner.

Thanks,
Matty

[Steve_P]

If it comes and goes at random, then look at leads, plugs, sockets, earthing and dry joints. Especially round capacitors or coils.

The setting up data is on sheet 1653.

Cheers,

Steve P.

[matthewhouse]

Ok, thanks will do, I also meant to say I'm using the 1653 sheet not 1652 like I posted before.

[Steve_P]

Tip from an Engineer.

Get something non-conductive (such as a pen case!) and tap around, try and make it come and go at will.

Cheers,

Steve P.

[Mr Hoover]

Originally Posted by matthewhouse

Thanks for the quick reply, tried reducing the power but no help, this fault intermittently clears itself.

Looking at the 1652 sheet it appears to use the alternative tuner.

Thanks,
Matty

I've had intermittent type problems with the germanium IF transistors
(think AF117 type,circuit not to hand) in this set.
Try tapping the case of each one very hard and see if it
can make the fault come and go.

Hugh

[matthewhouse]

Thanks, I believe the fault is in the top corner of the if/frame timebase panel there is a AF114 tapping that one causes the ripples to go temporarily. Ill stick a new one in here and see what happens. Ive resoldered that whole area.

[matthewhouse]

Originally Posted by Steve_P

Try reducing the RF power output from the 405 Converter. It may be too high.

You were right, an attenuator was fitted and the problem stopped, only slight attenuation was needed to cure the fault. There was not a problem with the set at all. The loud frame buzz on the sound has also gone too. It is currently under test now.

Thanks for everyones help,

Matty