Kolster Brandes WV-05

[chompy1]

ah! Good point Brian! The CRT is a 19" and I have got a five stick tripler fitted to it at the moment, so that's what it must be.

Unfortunately, I don't have any spare 3 stick triplers

would I be able to use a high wattage resistor to bring the amperage down?

[Focus Diode]

Hi Paul,

I would very strongly advise against any attempts to reduce the EHT voltage using resistors.

The best solution would be to place a request for a 3-stick EHT tray in the "Sets and Parts Wanted" section. If the tray is an "open" type it would be possible to modify it to a 3-stick unit but it was never advisable to modify or carry out repairs to a unit as this could introduce undesirable problems such as corona etc.

It would be best to keep the 5-stick tray as a spare for your 24" 1400 and to obtain the correct 3-stick EHT tray which would also be far safer. I'm sure someone on the forum could assist in helping you out with one.

Unfortunately I don't have a spare 3-stick unit myself but could do with one too.

Cheers,
Brian

[chompy1]

ok, thanks Brian. Is the 1500 one of the Thorn models that uses a 3 stick tripler?

Cheers, Paul

[Focus Diode]

Originally Posted by chompy1

Is the 1500 one of the Thorn models that uses a 3 stick tripler?

Yes, the 20" models have a 3-stick EHT tray. A 5-stick unit is fitted to 24" models.

Cheers,
Brian

[FERNSEH]

Hi Paul,
I've found a three stick EHT doubler. Let me know if you want it?

DFWB.

[chompy1]

Hi Chaps,
I've now returned to this set. I've got it switched to 625 lines, and I've got a BRC 1500 L.O.P.T and doubler connected up to it, but all the CRT is displaying, is a very short and thin line of light in the center.

What are your thoughts?

Thanks, Paul

[Focus Diode]

Hi Paul,

Is the line vertical (frame/field) or horizontal (line) ? Either way both timebases need attention if the line fails to reach the screen edges. Whichever timebase has failed I would concentrate on the stage which has failed completely, be it line or frame, before finding out why it doesn't fill the screen.

It would be interesting to hear how you've adapted the 1500 LOPT to work in the set, not only out of interest but to also assist others who may wish try this LOPT transplant in a similar set.

Good to hear from you again.
Cheers,
Brian

[chompy1]

Hi Brian,
the line is horizontal. At the moment I'm just experimenting with BRC 1500 L.O.P.T.

I've got the top cap of the PL36 connected to pin A, the top cap of the boost diode connected to pin B, the chassis connected to pin D and the reference pulse connected to pin E.

Are there any changes I need to make?

Thanks, Paul

[FERNSEH]

Hi Paul, the Thorn 1500 Jellypot will simplify things a bit. Unfortunately the converted set will not work on 405 lines using this transformer, you'd need one removed from a 1400 or 950 series receiver for that.

Revised connection notes of the Jellypot conversion:

The PL36 top cap will go to tag A on the jellypot. B to the top cap of the boost diode PY81/800. D to earth. The 220pF tuning capacitor is connected between tags B and D. No tag C on 1500 transformers. The pulse feed capacitor to the width control VDR should go to tag H and the line scan coils can be connected to this point as well.
It's at the boost HT end of the line transformer where things get complicated.
Tag G is the Jellypot boost HT connection.
Reference to the KB circuit diagram: Connect all the leads that were connected to tag 11 to tag H of the jellypot.
There is a good chance that the reason the frame timbase has failed is because the boost supply to the height control has become disconnected.
For some reason the 700 volts boost supply to the width and height controls comes from a tapping on the original line output transformer. Find the wires to boost tag and reconnect them to tag G of the Jellypot.
This action might well restore the frame timebase operation.

I hope these notes help.

DFWB.

[FERNSEH]

The attached circuit diagram shows the connections to the boost capacitor C134 and R150. The 750volt supply. Reconnect everything from the boost tag of the original transformer to tag G of the jellypot.

A recent Jellypot conversion: https://www.vintage-radio.net/forum/...ht=Decca+DR123

DFWB.

[FERNSEH]

Originally Posted by chompy1

I've got the top cap of the PL36 connected to pin A, the top cap of the boost diode connected to pin B, the chassis connected to pin D and the reference pulse connected to pin E.

Hi Paul,
The reference pulse tag E on the Jellypot will not supply a high enough amplitude pulse for the width control. Connect C133 the feedback capacitor to tag H.
the winding on tag D and E was used for the flywheel sync reference in 1400 and 1500 TVs.

DFWB.

[FERNSEH]

Correction to my post #49. Those boost HT connections to the original KB transformer tag 11 should go to Jellypot tage G.
The 625 S correction capacitor C128 should go to Jellypot tag G.

DFWB.

[chompy1]

Thank you for all the info David. It is much appreciated. Hopefully I will have time to have a go at it tomorrow eve.

On the original transformer, there is an orange wire connected to the bottom coil. Is this wire for the 405 lines side of it?

I'm well impressed with the results of your work on your DR123, It looks great!

Thanks, Paul

[FERNSEH]

Hi Paul,
I think that the orange lead connects to C131, the 405 S correction capacitor.
The part of the circuit that causes particular concern is the reference pulse feedback to the line sync discriminator. It may be necessary to employ the Jellypot winding D E instead of the existing arrangement where the pulse is taken from the "top" of the line output transformer via S15 and S16.

DFWB.

[FERNSEH]

My suggested circuit for the line output transformer substitution.
I think where we might have problem is the polarity of the feedback pulse to the line sync diodes. If that proves to be the case then the winding on tags D and E can be employed for the ref.pulse. That's how it is done in the 950 and 1400 receivers.
If converting a fully dual standard set then the 405 S correction capacitor C131 will be connected to tag C of the Jellypot.
The 625 S capacitor C128 goes to tage H. Also, the width control feedback capacitor C133 is connected to tag H or if it is more convenient to the switched end of C128. It follows that the S correction capacitors remain connected to system switch S16.
Note that PL36 screen grid switch has been transfered to select the additional 600pF 4KV 405 LOPTx tuning capacitor.

DFWB.

[chompy1]

Hi Everyone,
I was playing around with the tuning side of the set this weekend, and I managed to get it to tune into free view on 405 lines through the aurora, but it wouldn't tune into the free view on 625 lines, so I guess the VHF tuner is missing the 625 lines frequency biscuit?

My understanding of how valve circuitry works is limited, so when I first started on this set, it was a real mind boggler for me, and it still is, so to get this set up and running fully, I will need all the help I can get from everyone.

Thanks, Paul

[Focus Diode]

Unlike some models, eg BRC, which have a special UHF biscuit in the "U" posistion I don't think the KB models have these. The system switching is by a separate control and not ganged to the VHF tuner.

The VHF tuner does provide amplification to the UHF side, though a fault here can affect UHF as well as VHF. An example I had was a clean raster with no signals on UHF due to the PC97 valve in the VHF tuner!

If all seems well on VHF the UHF tuner could be responsible. I think a valved type is fitted to your set. Replacement valves should be tried as a first step.

Hope that's some help.
Cheers,
Brian

[HamishBoxer]

PC88 PC86 were always favorite for failing.

[chompy1]

thanks guys. The sets UHF tuner is a valved tuner and does employ a PC88 and a PC86, so my next step will be to try a NOS PC88 and a NOS PC86.

Are there any capacitors or resistors that are prone to becoming O/C or S/C on this set?

Thanks, Paul

[dazzlevision]

Hello,

The UHF IF input to the VHF tuner's mixer stage is via a "bridge" circuit, which requires no (internal) VHF tuner UHF/VHF switching or a "UHF" turret biscuit in the VHF tuner.

On UHF/625, the long system switch on the main chassis removes the HT to the VHF tuner's local oscillator and connects HT to the UHF tuner. The pentode section of the VHF tuner mixer/osc valve then acts as an additional IF amp stage.

Regards,

Dazzlevision