Tandberg Solvsuper 3 (1941)

[Geordie McBoyne]

From the Radiomuseum, the EFM1: http://www.radiomuseum.org/tubes/tube_efm1.html

and the EM4: http://www.radiomuseum.org/tubes/tube_em4.html

EF92 is a good replacement for the EF39. EF39 gm = 2.2mA/V. EF92 = 2.5ma/V.

Geordie McBoyne.

[Refugee]

Is the AM waveform clipped before it gets to the detector diode?

[Murphyv310]

Hi.
I've tacked in an EF92 and the issue has been cured, I suspect the grid leak on the pentode section was dragging the AGC more positive. I now have minus 10v on strong signals. Next will be to wire up the EM4 and do a permanent fixture for the EF92.

[Murphyv310]

Hi.
Well I have two jobs to do on the set. Since yesterday I have fitted the EM4, it's dull even though it is NOS, it will remain in the meantime though.
Next is to do will be the cabling to the speaker enclosure, the feed to the energising magnet and the low impedance output from the transformer to the speech coil, I've some good quality cable from a car loom that will be utilised.
The other job will be to find a suitable mounting point for the EF92 and neatly running the wiring to the modification. The chassis is fairly crowded so an alternative will have to be used.

For a wartime set I am really impressed with it's performance, I'd say it's down to the quality of the tuned circuits and IF transformers, it is unbelievably sensitive, the combined tone/bandwidth control works well with pin sharp tuning and only a small drop in fidelity on position 1 which is the narrowest setting, Short wave is lively and drift free, Long wave was interesting today as Allouis has re-appeared after being off yesterday, perhaps it's had a stay of execution???

[Murphyv310]

                       

Hi. Most of the work is now done, at a later date I'll substitute an EM34 instead of the rather down EM4 (NOS). I've replaced the perished speaker cables and since taking the pictures tidied the mains cable and added a filter cap, this helps to reduce the tendency for modulation hum.
One of the biggest issues this set had was the trimmers, they are ceramic and have an odd arrangement for adjustment, nearly everyone was faulty, corrosion seems to have killed them, having a box of modern trimmers (2-30 & 5-55pf versions) I have tacked these on to the originals after removing the corroded parts, a second realignment was carried out and the tracking on all bands is uncannily accurate.
Unfortunately the set is now not original and the chances of robbing another for the parts is highly unlikely, due to this I have not restuffed the capacitors.
My feeling is that this rare set has now a new lease of life and once my friend who has taken unwell (got the cabinet back unfinished) who was going to refurbish the cabinet is all done this set will take pride of place in my collection.
I cannot praise the set enough, the sensitivity is like a set with an RF stage, on selectivity position 1 it is better than I previously thought. My local on 1035 usually floods Downtown radio (Belfast) on 1026Khz and 1.7Kw is perfectly listenable.
So this has been a really great set to do and the significance of the set being made in 1941 to me is really important.

Once the cabinet has been done I'll post up the pictures.

[Geordie McBoyne]

Hi Trevor,
I notice that the mains voltage carousel looks like a Philips component. It's possible that the tuning inductors and IF transformers were also sourced from Philips.

Geordie McBoyne.

[Crackle]

Interesting it has a separate sealed speaker compartment, almost like a 70s speaker with the glass wool absorbent mat.

Mike

[Murphyv310]

Hi Mike
The audio quality must rank as one of the very best, Tandberg were always well known for their quality. This set sounds like an FM set.

David , the small PF value caps are marked Germany and there was the black Philips caps too.

[Murphyv310]

Hi.
Here is a little video of the set taken about 12:30 today.
It might give some idea about how well it performs.
https://youtu.be/Gn6ym1LtTfM

[Crackle]

Hi Trevor
The audio quality is very good when there is a strong signal, the variable bandwidth looks useful.

Mike