Grundig 2035W/3D/GB

[Mike Watterson]

This arrived on Thursday from a nearby person.
There are two versions of the German model, one with an EC92 and one with ECC85, this model has the ECC85. Main differences seem to be the extra pilot lamp to either indicate MW & LW, or that the ferrite rod aerial is in circuit.


A burnt wirewound resistor and a small pilot bulb rolled out when I set it on the kitchen table while I went to clear a space.


I started at 7 pm last night.
Loads of paper caps. One was crisped and had a 25 Ohm resistor beside it to chassis. The cathode of EL84? But no it was the screen grid pin 9. Pin 3, cathode, had the correct 170 Ohms. So I removed it as it couldn't be right. That's an HT rail.

Replaced 6 paper caps and put the 25 Ohms in series with rectifier (the metal one had been replaced).

Puzzled over VHF drive cord after refitting it. Not snapped, just off. A lever on piano keys engages AM or VHF drive cord to single tuning cord. AM cursor would jam. Cord was off the red flag of tone control, but not snapped. Fixed that after removing scale glass.

Refitted mysterious second small pilot bulb using a holder arrangement I'd not seen. Removed all the panel dust and refitted scale & knobs.

Powered up. No Glow on EM81, no hum. But more than 300V on an audio transformer pin.

Stared at chassis. Where is the 1300 Ohm resistor between audio transformer and secondary HT rail? Where is that transformer wire?

Remembered loose cut off burnt out resistor. About 1/2 way from one end was 700 Ohms. So the 1300 Ohms part. It MIGHT have connected to pin 9 on EL84 base. There is a tag with a yellowish wire on the fuse/voltage selector panel. Pokes and tugs here and there reveal it's from the audio transformer and goes nowhere else.
I fit 1K in series with 100 R from wire to secondary HT and now there is hum on Gram, loud if socket touched. Green glow at base of EM81. For a moment I'd thought the audio transformer was burnt out and it's got 4 connections on primary and a feedback winding.

No LW, MW, SW or VHF. Swapped EF89 and then ECH81. Don't think I've an ECC85 or EABC80, but maybe something else wrong as so dead. After 11 pm so no more tonight.

Maybe later on Saturday I'll look at it again and logically trace HT & IF.

The GB version I have https://www.radiomuseum.org/r/grundig_3d...w3dgb.html
The German schematic I'm using https://www.radiomuseum.org/r/grundig_2035ws3d.html though I already had it on the laptop from years ago from Dutch

[Mike Watterson]

Any thoughts as to why Radio mode is so dead?

Edited version of DE domestic version from NVHR. Very similar. Main differences are the 240V input position and extra winding for switched 100mA pilot lamp at volume control.
Electrotanya has the older EC92 version
   

I'll check the 4uF (+ to chassis of course) on EABC80 for FM, but total lack of any AM too is odd, esp with ECH81 and EF89 swapped. The EABC 80 triode is working and the AM diode doesn't usually fail.

All the AM and FM IFTs are in series, so if one winding anywhere is open circuit then no IF (except on final detector drive).

[Mike Watterson]

I turned it on on LW and was greeted by typical interference buzz. Nothing when switched to ferrite rod. Connected up sig gen and the LW, MW, & SW is close enough correct. Perhaps the ferrite/external switch above chassis was jammed in ferrite position. See below.

Nothing on VHF.
However no surprise it doesn't get RTE R1 252 kHz (is it even on today?) or BBC R4 198 kHz as it's very deaf.

Replaced the 4uF 80V electrolytic with 2x 2.2uF 100V in parallel (you'd want maybe at least 35V here) taking care that + ends to chassis.
Now there is very weak VHF.

So at least some progress. No difference between my spare EL84, EF89 and ECH81 and the originals. Cleaned and oiled jamming mechanics on AD switch. Reason for pilot ls that the switch above the chassis is a push-on/push-off type and thus the piano key button isn't meant to stay down, so lamp is only indication of external or internal ferrite aerial. Also off on PU, SW and VHF.

A poor ECC85 usually means no reception at all? Stops oscillating.

Perhaps there is an open circuit IFT connection? That sometimes still works but with very poor sensitivity. That will be the next thing to check?

[Mike Watterson]

Well, I thought I'd take a quick look with the DMM across the IFTs.

I looked at the first and discovered a loose wire that was near the earth pin of the DIN 3 way socket, which has the "play" directly connected to Gram socket. I traced it back and it went to loads of pins of the base and centre of the EF89 socket!

Ah Ha!!!!

Soldered it instead to nearby chassis tab.

Powered on and VHF-FM stations all blasting in! The EM81 is a bit dim but closes almost completely on a strong station. Our electric is closer to 230 than 220, so I have it on the 240V for longer life.

So I wasn't wrong about final fault being around the IF. Also picking up some non-English station with 2m of wire near HF end of Shortwave, so ECH81 is OK. It goes LOUD. Tone controls work.

The grid leak on the EABC80 triode is 10 M ohm and the series cap goes to the volume control wiper, so though no HT, leakage might be an issue. It's inaccessible, 10nF, so I snipped end at the the valve base and put a 100 nF ceramic cap. Now no faint crackle on volume control.

I wonder how such a set (made for launch of UK VHF-FM) ended up in Co. Limerick? Probably no VHF here (radio or TV) till Dec 1961 or Jan 1962. Even then you'd have needed a good aerial in Limerick City as the TX choice was Mullganish or Maghera. Must have been late 1980s or early 1990s, I forget, when Limerick City, Shannon Estuary and nearby Clare and Limerick got a local mast at Woodcock. You can get Limerick's Live 95FM nearly as far as Portlaoise now.

[Mike Watterson]

Conclusions:
Never plug in second hand old stuff without internal examination.
Thick layer of undisturbed dust doesn't mean it wasn't got at.
You need rich customers to restore stuff for others at even a minimum wage.
How many radios do you need anyway?

Got some UK MW stations on it after dark on internal rotatable ferrite. You certainly are not going to rotate the radio.
SW is lively with 2m of wire hung from curtain rail end.
Need to take it apart sometime as centring the  shafts on scale holes is wrong, you need to line up glass print to the piano keys.

Issue
Slight mains leakage to external metal work even when off needs investigated. It's a single pole mains switch and single insulated two core mains cable, brown plastic figure-of-eight style as was typical.
Either fit 3 core cable or coded 2 core. Check mains transformer, maybe soak in polyurethane or replace as I have one off an old Philips that might do. Could be leakage on fuse board. The on-off switch looks like a regular toggle type adapted for the piano key mechanism.

[Mike Watterson]

For now till I investigate further I reversed the mains at the plug. Now no leakage on or off to chassis or metal work. But obviously needs examined & 3 core flex fitted after isolation to either mains connection is sorted.

[Mike Watterson]

Replaced  twin unmarked mains lead with light-weight 3-core mains with blue, brown & yellow/green cores. Live to switch terminal on fuse & tag board and neutral to common of voltage selection fuses. The tag board a bit cooked at bottom likely due to he screen cap (just under it) burnt by 1300 Ohm resistor burnt out (one end to Audio TX on tag, other end to EL84 Screen Grid / secondary HT. I have that resistor differently mounted now. That's the same wiring for mains as when I reversed the cable at the plug which improved LW. Adding an earth makes LW worse, common.

Often radios with live chassis and single pole switch on the volume control have switch to chassis to reduce hum. Wires here from tag board with fuses to switch are a twisted pair. No noticeable change in hum with live to switch on this set.

Final Tally
9 paper caps removed and replaced. One between volume slider and EABC80 triode grid got cut at valve base and a 0.1uF ceramic fitted as it was too difficult to remove. Other caps on tone controls left as no HT etc.
1 Electrolytic replaced, a 4uF 80V on FM discriminator with 2 x 2.2 uF 100V in parallel. The +ve to chassis.
25 Ohm that was retrofitted between earth tag and screen grid tag of EL84 removed. The tag with the audio transformer winding is nearby, so obviously fitted in error to replace the burnt out 1300 Ohms. I put the 25 Ohms in series with the silicon bridge someone had fitted instead of original "metal rectifier" (probably typical German selenium type).
Fitted 1000 Ohms on unused tag near secondary HT 50uF cap tag and other end to yellow audio transformer wire with heatshrink sleeve. Add 100 Ohms between tag and 50uF +Ve tag. The total 1100 Ohms is close enough to the original 1300 for secondary HT line and EL84 Screen grid.
Refitted VHF drive cord and treble flag drive cord. Neither broken, just off.
Refitted loose part & bulb of the AD switching lamp at rod rotation knob.
Freed up seized AD switch push-on/ push-off switch (Ferrite rod or socket).
Wiped case and picked off gratuitous clear sticky tape.
Replaced two core flex by three core and earthed chassis.