22-07-2020, 09:54 PM
(This post was last modified: 22-07-2020, 10:02 PM by Mike Watterson.)
It's very challenging when you've no schematic or alignment information and it's more than one wave band. I always find multiband (more than MW & LW) coil / switch units hard to reverse engineer.
Now that's it's dusk the MW is getting lively and some stations on OC2 (49m to 20) quite loud just with a temporary "whip". The RF SW coil is nearly fully out to peak, so I'll check SW LO setting on OC1 as OC2 just uses the same coils. One station at the 40m end of OC1 and a loud Arabic one at 3/4 way to the 20m upper limit of OC1, the higher SW band.
I was very suspicious of the 33K HT feed resistor to LO coil/switch pack as two SM caps had obviously been re-soldered and two SM caps had snapped leads. Always hard to see where a stray MW coil wire and stray LW coil wire came off when they are Litz. I got confidence when there was SOME life on MW, but it couldn't work properly on the other bands with the resistor going to the MW coil tag, hence willingness to take out the IFTs and all the SM caps and trace it somewhat.
Also early on it was evident something was wrong on the secondary of the 2nd IF. No doubt the selectivity would be slightly better if Litz had been used, but I counted the wire I unwound.
So in addition to all the original listed issues:
One IFT coil needed rewound.
All the wires had to be redone on the B7G plug of the power connector, and the socket holes attacked with the finest Dremmel cone in/out by hand. Works better than spinning it with the tool.
The HT feed 33K to LO coil/switch pack was on the wrong tag. It had full length leads and was folded up. The correct tag is close to the point on the DF96 were it's soldered to.
Two intermittent connections
Resistors and caps
I've never replaced so many resistors or Silver mica caps, ever.
150, 330, 1M, 2 x 2M2, a 47k gone to nearly 80K, 3M3, 33K. I think only the 10M DAF96 grid leak and the DK96 osc g1 27K to f+ are original.
One SM was OK.
Three had small (10 to 33 pF) ceramic caps soldered across the back.
One Silver Mica replaced because every time I soldered it the value reduced. It was labelled 106PF or 105PF, started at 86 and went down to 62! Replaced with 100 + 10, which was 1pF higher only than label. I think 177 pF might really be a design of 180pF and 106 pF a 100pF? My theory is that the caps were marked with actual test value to nearest 1 pF before coating in wax. The white paint is on the main paxolin substrate. The other outer layer is very thin.
There are 3 spots near the closed end of the LO tuning cap that short. It's OK fully closed. So fine dry "wet & dry" paper and gently sand before final alignment. I must polish and varnish the actual brass pointer so it's visible against the black hard board.
I've seen the PSU circuit for the older 5 band Club that uses the DK92. It's on DocTSF . An autotransformer for HT of about 82V and LT of 8V. The 8V dropped to 6.2V. Then that's folded on 2 x 1.5 D cells for battery, with the 8V to 6.2V dropper resistor across the battery!
The model I have ominously has the isolating capacitor on the Terre (Earth) socket, but a weird glass thing that looked home made from a glass fuse (it seems to be a capacitor) had its covered wire enter the Earth socket and was soldered to the Ant socket. Surely that wasn't original?
I presume the Ant socket connected to the same place as the telescopic whip, which doesn't seem isolated! So perhaps that mysterious capacitor fed the whip too. The whip does seem to connect on LW & MW, via switch contacts, as well as the OC1 and OC2.
I've no idea how representative of French battery portable valve radios this is. I had French 1962 approx AM/FM mains set and the only odd aspect was a tall rotating card cylinder with LW & MW loop coils at right angles and at right angles to that a loose helical wire. Also the VHF tuner head used an ECF82 which I'd not seen before. Otherwise it was quite like a German set.
Now that's it's dusk the MW is getting lively and some stations on OC2 (49m to 20) quite loud just with a temporary "whip". The RF SW coil is nearly fully out to peak, so I'll check SW LO setting on OC1 as OC2 just uses the same coils. One station at the 40m end of OC1 and a loud Arabic one at 3/4 way to the 20m upper limit of OC1, the higher SW band.
I was very suspicious of the 33K HT feed resistor to LO coil/switch pack as two SM caps had obviously been re-soldered and two SM caps had snapped leads. Always hard to see where a stray MW coil wire and stray LW coil wire came off when they are Litz. I got confidence when there was SOME life on MW, but it couldn't work properly on the other bands with the resistor going to the MW coil tag, hence willingness to take out the IFTs and all the SM caps and trace it somewhat.
Also early on it was evident something was wrong on the secondary of the 2nd IF. No doubt the selectivity would be slightly better if Litz had been used, but I counted the wire I unwound.
So in addition to all the original listed issues:
One IFT coil needed rewound.
All the wires had to be redone on the B7G plug of the power connector, and the socket holes attacked with the finest Dremmel cone in/out by hand. Works better than spinning it with the tool.
The HT feed 33K to LO coil/switch pack was on the wrong tag. It had full length leads and was folded up. The correct tag is close to the point on the DF96 were it's soldered to.
Two intermittent connections
Resistors and caps
I've never replaced so many resistors or Silver mica caps, ever.
150, 330, 1M, 2 x 2M2, a 47k gone to nearly 80K, 3M3, 33K. I think only the 10M DAF96 grid leak and the DK96 osc g1 27K to f+ are original.
One SM was OK.
Three had small (10 to 33 pF) ceramic caps soldered across the back.
One Silver Mica replaced because every time I soldered it the value reduced. It was labelled 106PF or 105PF, started at 86 and went down to 62! Replaced with 100 + 10, which was 1pF higher only than label. I think 177 pF might really be a design of 180pF and 106 pF a 100pF? My theory is that the caps were marked with actual test value to nearest 1 pF before coating in wax. The white paint is on the main paxolin substrate. The other outer layer is very thin.
There are 3 spots near the closed end of the LO tuning cap that short. It's OK fully closed. So fine dry "wet & dry" paper and gently sand before final alignment. I must polish and varnish the actual brass pointer so it's visible against the black hard board.
I've seen the PSU circuit for the older 5 band Club that uses the DK92. It's on DocTSF . An autotransformer for HT of about 82V and LT of 8V. The 8V dropped to 6.2V. Then that's folded on 2 x 1.5 D cells for battery, with the 8V to 6.2V dropper resistor across the battery!
The model I have ominously has the isolating capacitor on the Terre (Earth) socket, but a weird glass thing that looked home made from a glass fuse (it seems to be a capacitor) had its covered wire enter the Earth socket and was soldered to the Ant socket. Surely that wasn't original?
I presume the Ant socket connected to the same place as the telescopic whip, which doesn't seem isolated! So perhaps that mysterious capacitor fed the whip too. The whip does seem to connect on LW & MW, via switch contacts, as well as the OC1 and OC2.
I've no idea how representative of French battery portable valve radios this is. I had French 1962 approx AM/FM mains set and the only odd aspect was a tall rotating card cylinder with LW & MW loop coils at right angles and at right angles to that a loose helical wire. Also the VHF tuner head used an ECF82 which I'd not seen before. Otherwise it was quite like a German set.
