Perdio Portarama MKII Vertical Lock and Height - UK Vintage Radio Repair and Restoration Discussion Forum

af024 · 6th Jun 2006, 9:12 pm

Here’s a bit of a problem. I’m working on my Perdio Portarama MK2 (Trader 1652/T258) and I’m afraid that I’ve about run out of ideas.

In short, vertical lock is very very touchy indeed. Once tiny knock of the Frame Hold control and the picture is rolling.

The supplies have all been set up as per the procedure and everything is looking ok in that regard.

I initially thought that there would be a problem with the sync separator – but it doesn’t look that way. Frame sync pulses also look ok, so what on earth is going on?

Additionally I am at the limit on height adjustment (flat out). R140 not high in value.

I have 10.2Vd.c. across C128, 9.8Vd.c. at the junction of VDR101 and TR112 collector and 0.01Vd.c across TH100.

I have scoped a few areas as follows:-

Trace A is taken at the wiper of VR103. ‘Scope settings were 2V/div, centre line is 0V, TB 5mS/div.

Trace B is taken at the base of TR111. ‘Scope settings were 5V/div, centre line is 0V, TB 5mS/div.

Trace C is taken at the collector of TR111. ‘Scope settings were 5V/div, centre line is 0V, TB 5mS/div.

Trace D is taken at the emitter of TR112. ‘Scope settings were 0.5V/div, centre line is 0V, TB 5mS/div. The same trace is obtained at the emitter of TR113.

Not connected with the problem I know, but the exploded mechanical view of the underside of the top control panel shows a capacitor located adjacent to VR400. It claims it to be C113, but this seems a bit wrong to me, isn’t it C406?

Also, R139 appears to be missing from the I.F/Timebase panel. My set has it located just to the right of T107 - between it and C129.

Anyhow, I’d really appreciate some ideas on what’s causing both faults ‘cause it’s now driving me mad.

Many thanks.

Regards,

Andy

Heatercathodeshort · 8th Jun 2006, 12:38 am

Hello,
It is often much easier to lock the higher frequency line timebase than the lower frame. As a general rule check the base bias components of the sync separator transistor and then go back to the emitter components of the video amp. This can be very confusing when the line appears to lock 'solid'. Regards John.

af024 · 8th Jun 2006, 6:50 pm

John,

Thanks for your reply. I thought it was trying to lock on the frame as opposed to the line. I must take another look at the scope horiztontal timebase. I wonder how it can manage to lock on the line? Anyhow, the checks you suggest seem perfectly reasonable so I'll have another look in those areas. I wonder if the height amplitude problem is connected in some way?

Regards,

Andy

oldeurope · 9th Jun 2006, 7:46 am

Hi Andy, I don't have this set and I don't have this trader sheet.
But, verify that your source is ok. Are the sync tips all on the same level
after the vision detector? (Trigger on LINE(=ACmains), timebase 5ms/div and
look for the V-sync.)
What converter do you use?

Kind regards
Darius

af024 · 9th Jun 2006, 5:22 pm

Darius,

I'm using a 'Lil'Dino' modulator with a Dinosaur test card generator. I've even tried it with a new Aurora. The result is the same. My other sets behave ok.

I just need to work out where you suggesting I monitor with the 'scope. So much easier with the service sheet in front of you I know.

Now let me see ...

6th Jun 2006, 9:12 pm	#1
af024 Octode Join Date: Jan 2003 Location: Ashby-de-la-Zouch (it's not by the sea) Posts: 1,255	Perdio Portarama MKII Vertical Lock and Height Here’s a bit of a problem. I’m working on my Perdio Portarama MK2 (Trader 1652/T258) and I’m afraid that I’ve about run out of ideas. In short, vertical lock is very very touchy indeed. Once tiny knock of the Frame Hold control and the picture is rolling. The supplies have all been set up as per the procedure and everything is looking ok in that regard. I initially thought that there would be a problem with the sync separator – but it doesn’t look that way. Frame sync pulses also look ok, so what on earth is going on? Additionally I am at the limit on height adjustment (flat out). R140 not high in value. I have 10.2Vd.c. across C128, 9.8Vd.c. at the junction of VDR101 and TR112 collector and 0.01Vd.c across TH100. I have scoped a few areas as follows:- Trace A is taken at the wiper of VR103. ‘Scope settings were 2V/div, centre line is 0V, TB 5mS/div. Trace B is taken at the base of TR111. ‘Scope settings were 5V/div, centre line is 0V, TB 5mS/div. Trace C is taken at the collector of TR111. ‘Scope settings were 5V/div, centre line is 0V, TB 5mS/div. Trace D is taken at the emitter of TR112. ‘Scope settings were 0.5V/div, centre line is 0V, TB 5mS/div. The same trace is obtained at the emitter of TR113. Not connected with the problem I know, but the exploded mechanical view of the underside of the top control panel shows a capacitor located adjacent to VR400. It claims it to be C113, but this seems a bit wrong to me, isn’t it C406? Also, R139 appears to be missing from the I.F/Timebase panel. My set has it located just to the right of T107 - between it and C129. Anyhow, I’d really appreciate some ideas on what’s causing both faults ‘cause it’s now driving me mad. Many thanks. Regards, Andy Attached Thumbnails __________________ Now where on earth did I remove that from?

8th Jun 2006, 12:38 am	#2
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Perdio Portarama MKII Vertical Lock and Height Hello, It is often much easier to lock the higher frequency line timebase than the lower frame. As a general rule check the base bias components of the sync separator transistor and then go back to the emitter components of the video amp. This can be very confusing when the line appears to lock 'solid'. Regards John.

8th Jun 2006, 6:50 pm	#3
af024 Octode Join Date: Jan 2003 Location: Ashby-de-la-Zouch (it's not by the sea) Posts: 1,255	Re: Perdio Portarama MKII Vertical Lock and Height John, Thanks for your reply. I thought it was trying to lock on the frame as opposed to the line. I must take another look at the scope horiztontal timebase. I wonder how it can manage to lock on the line? Anyhow, the checks you suggest seem perfectly reasonable so I'll have another look in those areas. I wonder if the height amplitude problem is connected in some way? Regards, Andy __________________ Now where on earth did I remove that from?

9th Jun 2006, 7:46 am	#4
oldeurope Retired Dormant Member Join Date: Dec 2003 Location: Solingen, Germany Posts: 727	Re: Perdio Portarama MKII Vertical Lock and Height Hi Andy, I don't have this set and I don't have this trader sheet. But, verify that your source is ok. Are the sync tips all on the same level after the vision detector? (Trigger on LINE(=ACmains), timebase 5ms/div and look for the V-sync.) What converter do you use? Kind regards Darius

9th Jun 2006, 5:22 pm	#5
af024 Octode Join Date: Jan 2003 Location: Ashby-de-la-Zouch (it's not by the sea) Posts: 1,255	Re: Perdio Portarama MKII Vertical Lock and Height Darius, I'm using a 'Lil'Dino' modulator with a Dinosaur test card generator. I've even tried it with a new Aurora. The result is the same. My other sets behave ok. I just need to work out where you suggesting I monitor with the 'scope. So much easier with the service sheet in front of you I know. Now let me see ... __________________ Now where on earth did I remove that from?