Grundig 4192 Stereo Radio - UK Vintage Radio Repair and Restoration Discussion Forum

berntd1 · 6th Dec 2009, 6:17 am

Hello all,

I am new here. I just bought a Grundig 4192 Radio.

Is this the same a a Grundig Majestic 4192 ?

Are these collectable and should I repair it or leave it as found original?
Do they sound nice when working?

It appears in reasonable condition but of course it is not working. In fact, I havn' t even tried it because I don't want to blow up any old caps.

Does anyone know or have a schematic for it perhaps?

Kind regards
Bernt

jjl · 6th Dec 2009, 11:00 am

Hello Bernt

Is this

http://www.radiomuseum.org/r/grundig...92_stereo.html

the same as your radio?

If so, it is definitely worth restoring. Grundigs are fantastic sets but can be a bit challenging to restore. Do you have much experience?

John

georgesgiralt · 6th Dec 2009, 12:31 pm

Yes, it is worth restoring.
It has a few peculiarities, though. The double output penthode, ELL80 and the electrostatics speakers.
If you search the Radiomuseum site forum, you'll find a DIY post explaining how to restore the speakers if needs arose.
As usual, check the filtration caps and THAT caps.
As for the ELL80 it is made from a couple EL95 in one bottle, so you can devise an adapter if you have trouble finding a working one.
sound is VERY good once put in working order.
Have fun.

georgesgiralt · 6th Dec 2009, 12:34 pm

Forgot something ...

JimMac53 · 6th Dec 2009, 4:12 pm

It's probably stereo only from the inputs in the back. FM is mono. That said, it's still worth restoring and it'll sound great. It will be nice to use with an ipod or mp3 player.

georgesgiralt · 6th Dec 2009, 4:22 pm

Yes, FM is mono only. It does not have the plug for the Grundig stereo decoder. But it is a great radio and you can devise something with an MC1310 or similar ... buried into the wiring.

berntd1 · 7th Dec 2009, 3:23 am

Hello al

Thank you for the replies!

It looks exactly like the one in the radio museum pics - Cool!

I am an electronics engineer. I used to meddle with this old stuff as well as ham radio during the 80s and early 90s. i love the old electronics stuff and it is probably the main reason why I bnecame an endineer. Pity that everything changed since.

I am sure I can repair it but I really am tempted to also keep it in as original as possible condition.

Maybe it doesn't need any replacement valves. We shall see

Kind regards
Bernt

jjl · 7th Dec 2009, 10:13 am

Bernt

It may well not need any new valves but if it is old enough to use paper dielectric capacitors, most, probably all of these will need to be replaced. There will be quite a lot of these in your set. To avoid damage to the output valves and transformers, the first capacitors to replace are those coupling the output valve grids to the previous amplifier stage.
I've also known mains and waveband switches, metal rectifiers, valve holders and fuse holders to give trouble in Grundig sets of this vintage.

Good luck.

John

JimMac53 · 7th Dec 2009, 10:44 am

Bernt,

I don't have as much experience as some here in this forum, but there is a ton of practical information here as you'll quickly learn. You'll get many in agreement for keeping it as original as possible. So you'll find lots of information and advice for stuffing old paper capacitors and electrolytics. And likewise for the restoring the cabinet.

I have restored about a half a dozen Grundig's, no 4192, but all of about the same vintage. Generally, I've found the valves in good working order, but the paper capacitors are generally leaky and out of tolerance. You'll need to change them. The selenium bridge may be still working, but it's a ticking time bomb. Most folks replace it with modern silicon bridge or 4 diodes (with bypass caps). If it's the can type, then you can gut it and stuff the bridge/diodes in the can, keeping the same look. If you replace the bridge, you'll need a dropping resistor to get the HT right, since the modern silicon is more efficient than the old selenium.

For these late 50's and early 60's valve radios, I'm afraid I'm of the opinion that I want to keep the outside look as original as possible and likewise looking into the back of the cabinet. But below the chassis, I do what I want. Beneath the chassis you'll find the quality (and safety) of the construction to be haphazard at best. The folks who built these way back when weren't interested in making them look pretty.

Start by cleaning, cleaning, and cleaning. Replace the paper caps. Then get the power supply right, quickly followed by checking the cathode voltage of the power amplifier valve, which is a good indicator that it's bias is correct. Move forward from there checking the AM operation, then FM. That's my advice in a nutshell. Good luck.

Jim

berntd1 · 7th Dec 2009, 10:49 pm

Hello,

Thanks for all the great advice and encouragement!

What do paper capacitors look like? Are they the couplers between the different stages? I remember that in the really old sets, the caps were wax and cardboard tubes with foil. I seem to remember that the RF coupling was usually done with Mica caps or did they also use ceramic in 1960?

Right now, the major problems are with the mechanics. Both tuning cords are broken and the indicators may or may not be missing. The AM tuning cap is seized. The mechanical push switches all get stuck down halfway etc.

The ferrite antenna core was broken into 3 pieces and its wires are ripped from the coils. For now, I glued it back together with a bit of superglue. Luckily I found just about all the chips and pieces.

So what is the strategy for firing it up? Should I go cold turkey and switch it on through a suitable light bulb or something?

I could also remove the valves and then switch it on to measure the HT and heater voltages and I will certainly check the paper caps first.

Why does the replacement rectifier need four bypass caps? I have seen this but am not sure why.
I would have just replaced it with some 1000V diodes and maybe a resistor as you said.

Kind regards
Bernt

jjl · 8th Dec 2009, 1:14 am

1960 is around the time where German capacitor manufacturers such as Wima and ERO introduced plastic foil caps. Your set may or may not use paper capacitors but I'd be inclined to believe that there will be at least some lurking in there.
Paper capacitors in Grundig sets will be marked as "papier" on the schematic and will tend to have the appearance of cardboard tubes or be encapsulated in blue or brown resin.

How about posting some under-chassis photos then we can let you know which are likely suspects.

Paper capacitors were used for inter-stage coupling and decoupling, also in tone controls which can be quite complex in these sets.

Powering up with all of the valves removed via a lamp limiter is a good idea; it allows you to safely check for leakage in at least some of the coupling and decoupling capacitors.

You probably won't need bypass caps for each diode in the replacement bridge, these are only required when there is evidence of RF hash due to the diodes switching.

John

berntd1 · 8th Dec 2009, 10:14 am

Hello,

I will take pics of the inside as soon as I get the chassis out.

I managed to obtain the schematic for 4192 / 4198 Stereo.

Interestingly, it does not seem to correspond with what I have here.

My radio has BC, SW1 SW2 SW3 and FM. (see picture).
The schematic states LW, MW, KW, UKW (BC, AM, SW, FM)

Hmm...?

Kind regards
Bernt

JimMac53 · 8th Dec 2009, 11:04 am

I would hesitate to apply power until the coupling capacitors feeding power pentodes (the schematic I have shows 2) were replaced. If the bias on the output stage is incorrect, it can put the primary of the the audio transformers at risk (even with a lamp limiter). Regardless, I would monitor the cathode voltage of the output stage to ensure everything was okay (in addition to the HT). Cathode voltage should be in the neighborhood of 7-8 volts.

Here is some great capacitor information:
http://www.vintage-radio.com/repair-...apacitors.html
and:
http://www.radiomuseum.org/forum/rep...apacitors.html

However, I would probably address the mechanical issues before I dove into the electronics. The tuning capacitor could be a big issue and I'd want to know that it can be fixed before spending time (and money) on the other things.

jjl · 8th Dec 2009, 11:25 am

I agree that the mechanical problems may make this restoration impractical if they can't be solved.

Powering up with with a lamp limiter with valves removed is a useful diagnostic technique with sets using semiconductor rectifiers. There is no risk to output transformers as there are no output valves to pass current through them. Leakage in coupling capacitors can safely be tested by measuring the voltage between the grid end of the capacitor and chassis i.e. the capacitors will still leak even when no valve is fitted.

John

paulsherwin · 8th Dec 2009, 11:40 am

It looks as if you have the international export variant of this radio. These have one additional SW band replacing the LW band used in Europe, and the FM tunes all the way to 108MHz. Given the late start of FM broadcasting in Australia (1976?) it may have arrived via the US.

With regard to capacitors, your radio may have very early plastic film caps, but those early film Wimas aren't a lot more reliable than the old waxies. The simplest approach is to change all caps of 0.001uF or larger, which shouldn't take more than a couple of hours and will save lots of grief in the future. Any caps below this value will be ceramic or mica and are unlikely to be bad.

Paul

JimMac53 · 8th Dec 2009, 12:34 pm

Agree with all the comments above.

berntd1 · 8th Dec 2009, 10:24 pm

Hi all,

Is BC = MW ?

It is labelled 51 - 160 kc
Maybe they printed the scale incorreclty as MW is 510 - 1600 kc?

Kind regards
Bernt

jjl · 9th Dec 2009, 11:50 am

Yes, BC is a commonly used American term for medium wave. It stands for BroadCast. The dial markings of 51 to 160 kc are also consistent with this set being made for the American market.

John

paulsherwin · 9th Dec 2009, 12:06 pm

As a general rule, MW and LW are only marked on consumer equipment in territories where LW is used for broadcasting (Iceland, Europe, Russia, the Middle East and North Africa.) Elsewhere MW is just known as the 'Broadcast Band', abbreviated to BC.

I thought BC was used in Australia and NZ too, but I encounter few Australian radios so could well be mistaken.

Paul

berntd1 · 9th Dec 2009, 9:57 pm

Hello,

The radios I have seen, all have MW marked as AM.

That is the more moden ones. I don't know how vintage Australian radios were marked.

I have seen BC a few times but I seem to remember that it was on some vitage Becker car radios that I used to repair in the past.

Kind regards
Bernt

6th Dec 2009, 6:17 am	#1
berntd1 Retired Dormant Member Join Date: Dec 2009 Location: Sydney, Australia. Posts: 13	Grundig 4192 Stereo Radio Hello all, I am new here. I just bought a Grundig 4192 Radio. Is this the same a a Grundig Majestic 4192 ? Are these collectable and should I repair it or leave it as found original? Do they sound nice when working? It appears in reasonable condition but of course it is not working. In fact, I havn' t even tried it because I don't want to blow up any old caps. Does anyone know or have a schematic for it perhaps? Kind regards Bernt

6th Dec 2009, 11:00 am	#2
jjl Octode Join Date: Jan 2003 Location: Ware, Herts. UK. Posts: 1,082	Re: Grundig 4192 Stereo Radio Hello Bernt Is this http://www.radiomuseum.org/r/grundig...92_stereo.html the same as your radio? If so, it is definitely worth restoring. Grundigs are fantastic sets but can be a bit challenging to restore. Do you have much experience? John

6th Dec 2009, 12:31 pm	#3
georgesgiralt Hexode Join Date: Jul 2008 Location: Toulouse, France Posts: 406	Re: Grundig 4192 Stereo Radio Yes, it is worth restoring. It has a few peculiarities, though. The double output penthode, ELL80 and the electrostatics speakers. If you search the Radiomuseum site forum, you'll find a DIY post explaining how to restore the speakers if needs arose. As usual, check the filtration caps and THAT caps. As for the ELL80 it is made from a couple EL95 in one bottle, so you can devise an adapter if you have trouble finding a working one. sound is VERY good once put in working order. Have fun.

6th Dec 2009, 12:34 pm	#4
georgesgiralt Hexode Join Date: Jul 2008 Location: Toulouse, France Posts: 406	Re: Grundig 4192 Stereo Radio Forgot something ... Attached Thumbnails

6th Dec 2009, 4:12 pm	#5
JimMac53 Hexode Join Date: Apr 2009 Location: Naples, Florida, USA Posts: 255	Re: Grundig 4192 Stereo Radio It's probably stereo only from the inputs in the back. FM is mono. That said, it's still worth restoring and it'll sound great. It will be nice to use with an ipod or mp3 player. __________________ Jim Mac

6th Dec 2009, 4:22 pm	#6
georgesgiralt Hexode Join Date: Jul 2008 Location: Toulouse, France Posts: 406	Re: Grundig 4192 Stereo Radio Yes, FM is mono only. It does not have the plug for the Grundig stereo decoder. But it is a great radio and you can devise something with an MC1310 or similar ... buried into the wiring.

7th Dec 2009, 3:23 am	#7
berntd1 Retired Dormant Member Join Date: Dec 2009 Location: Sydney, Australia. Posts: 13	Re: Grundig 4192 Stereo Radio Hello al Thank you for the replies! It looks exactly like the one in the radio museum pics - Cool! I am an electronics engineer. I used to meddle with this old stuff as well as ham radio during the 80s and early 90s. i love the old electronics stuff and it is probably the main reason why I bnecame an endineer. Pity that everything changed since. I am sure I can repair it but I really am tempted to also keep it in as original as possible condition. Maybe it doesn't need any replacement valves. We shall see Kind regards Bernt

7th Dec 2009, 10:13 am	#8
jjl Octode Join Date: Jan 2003 Location: Ware, Herts. UK. Posts: 1,082	Re: Grundig 4192 Stereo Radio Bernt It may well not need any new valves but if it is old enough to use paper dielectric capacitors, most, probably all of these will need to be replaced. There will be quite a lot of these in your set. To avoid damage to the output valves and transformers, the first capacitors to replace are those coupling the output valve grids to the previous amplifier stage. I've also known mains and waveband switches, metal rectifiers, valve holders and fuse holders to give trouble in Grundig sets of this vintage. Good luck. John

7th Dec 2009, 10:44 am	#9
JimMac53 Hexode Join Date: Apr 2009 Location: Naples, Florida, USA Posts: 255	Re: Grundig 4192 Stereo Radio Bernt, I don't have as much experience as some here in this forum, but there is a ton of practical information here as you'll quickly learn. You'll get many in agreement for keeping it as original as possible. So you'll find lots of information and advice for stuffing old paper capacitors and electrolytics. And likewise for the restoring the cabinet. I have restored about a half a dozen Grundig's, no 4192, but all of about the same vintage. Generally, I've found the valves in good working order, but the paper capacitors are generally leaky and out of tolerance. You'll need to change them. The selenium bridge may be still working, but it's a ticking time bomb. Most folks replace it with modern silicon bridge or 4 diodes (with bypass caps). If it's the can type, then you can gut it and stuff the bridge/diodes in the can, keeping the same look. If you replace the bridge, you'll need a dropping resistor to get the HT right, since the modern silicon is more efficient than the old selenium. For these late 50's and early 60's valve radios, I'm afraid I'm of the opinion that I want to keep the outside look as original as possible and likewise looking into the back of the cabinet. But below the chassis, I do what I want. Beneath the chassis you'll find the quality (and safety) of the construction to be haphazard at best. The folks who built these way back when weren't interested in making them look pretty. Start by cleaning, cleaning, and cleaning. Replace the paper caps. Then get the power supply right, quickly followed by checking the cathode voltage of the power amplifier valve, which is a good indicator that it's bias is correct. Move forward from there checking the AM operation, then FM. That's my advice in a nutshell. Good luck. Jim __________________ Jim Mac

7th Dec 2009, 10:49 pm	#10
berntd1 Retired Dormant Member Join Date: Dec 2009 Location: Sydney, Australia. Posts: 13	Re: Grundig 4192 Stereo Radio Hello, Thanks for all the great advice and encouragement! What do paper capacitors look like? Are they the couplers between the different stages? I remember that in the really old sets, the caps were wax and cardboard tubes with foil. I seem to remember that the RF coupling was usually done with Mica caps or did they also use ceramic in 1960? Right now, the major problems are with the mechanics. Both tuning cords are broken and the indicators may or may not be missing. The AM tuning cap is seized. The mechanical push switches all get stuck down halfway etc. The ferrite antenna core was broken into 3 pieces and its wires are ripped from the coils. For now, I glued it back together with a bit of superglue. Luckily I found just about all the chips and pieces. So what is the strategy for firing it up? Should I go cold turkey and switch it on through a suitable light bulb or something? I could also remove the valves and then switch it on to measure the HT and heater voltages and I will certainly check the paper caps first. Why does the replacement rectifier need four bypass caps? I have seen this but am not sure why. I would have just replaced it with some 1000V diodes and maybe a resistor as you said. Kind regards Bernt Last edited by Darren-UK; 7th Dec 2009 at 11:42 pm. Reason: General tidying.

8th Dec 2009, 1:14 am	#11
jjl Octode Join Date: Jan 2003 Location: Ware, Herts. UK. Posts: 1,082	Re: Grundig 4192 Stereo Radio 1960 is around the time where German capacitor manufacturers such as Wima and ERO introduced plastic foil caps. Your set may or may not use paper capacitors but I'd be inclined to believe that there will be at least some lurking in there. Paper capacitors in Grundig sets will be marked as "papier" on the schematic and will tend to have the appearance of cardboard tubes or be encapsulated in blue or brown resin. How about posting some under-chassis photos then we can let you know which are likely suspects. Paper capacitors were used for inter-stage coupling and decoupling, also in tone controls which can be quite complex in these sets. Powering up with all of the valves removed via a lamp limiter is a good idea; it allows you to safely check for leakage in at least some of the coupling and decoupling capacitors. You probably won't need bypass caps for each diode in the replacement bridge, these are only required when there is evidence of RF hash due to the diodes switching. John

8th Dec 2009, 10:14 am	#12
berntd1 Retired Dormant Member Join Date: Dec 2009 Location: Sydney, Australia. Posts: 13	Re: Grundig 4192 Stereo Radio Hello, I will take pics of the inside as soon as I get the chassis out. I managed to obtain the schematic for 4192 / 4198 Stereo. Interestingly, it does not seem to correspond with what I have here. My radio has BC, SW1 SW2 SW3 and FM. (see picture). The schematic states LW, MW, KW, UKW (BC, AM, SW, FM) Hmm...? Kind regards Bernt Attached Thumbnails

8th Dec 2009, 11:04 am	#13
JimMac53 Hexode Join Date: Apr 2009 Location: Naples, Florida, USA Posts: 255	Re: Grundig 4192 Stereo Radio I would hesitate to apply power until the coupling capacitors feeding power pentodes (the schematic I have shows 2) were replaced. If the bias on the output stage is incorrect, it can put the primary of the the audio transformers at risk (even with a lamp limiter). Regardless, I would monitor the cathode voltage of the output stage to ensure everything was okay (in addition to the HT). Cathode voltage should be in the neighborhood of 7-8 volts. Here is some great capacitor information: http://www.vintage-radio.com/repair-...apacitors.html and: http://www.radiomuseum.org/forum/rep...apacitors.html However, I would probably address the mechanical issues before I dove into the electronics. The tuning capacitor could be a big issue and I'd want to know that it can be fixed before spending time (and money) on the other things. __________________ Jim Mac

8th Dec 2009, 11:25 am	#14
jjl Octode Join Date: Jan 2003 Location: Ware, Herts. UK. Posts: 1,082	Re: Grundig 4192 Stereo Radio I agree that the mechanical problems may make this restoration impractical if they can't be solved. Powering up with with a lamp limiter with valves removed is a useful diagnostic technique with sets using semiconductor rectifiers. There is no risk to output transformers as there are no output valves to pass current through them. Leakage in coupling capacitors can safely be tested by measuring the voltage between the grid end of the capacitor and chassis i.e. the capacitors will still leak even when no valve is fitted. John

8th Dec 2009, 11:40 am	#15
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,960	Re: Grundig 4192 Stereo Radio It looks as if you have the international export variant of this radio. These have one additional SW band replacing the LW band used in Europe, and the FM tunes all the way to 108MHz. Given the late start of FM broadcasting in Australia (1976?) it may have arrived via the US. With regard to capacitors, your radio may have very early plastic film caps, but those early film Wimas aren't a lot more reliable than the old waxies. The simplest approach is to change all caps of 0.001uF or larger, which shouldn't take more than a couple of hours and will save lots of grief in the future. Any caps below this value will be ceramic or mica and are unlikely to be bad. Paul

8th Dec 2009, 12:34 pm	#16
JimMac53 Hexode Join Date: Apr 2009 Location: Naples, Florida, USA Posts: 255	Re: Grundig 4192 Stereo Radio Agree with all the comments above. __________________ Jim Mac

8th Dec 2009, 10:24 pm	#17
berntd1 Retired Dormant Member Join Date: Dec 2009 Location: Sydney, Australia. Posts: 13	Re: Grundig 4192 Stereo Radio Hi all, Is BC = MW ? It is labelled 51 - 160 kc Maybe they printed the scale incorreclty as MW is 510 - 1600 kc? Kind regards Bernt

9th Dec 2009, 11:50 am	#18
jjl Octode Join Date: Jan 2003 Location: Ware, Herts. UK. Posts: 1,082	Re: Grundig 4192 Stereo Radio Yes, BC is a commonly used American term for medium wave. It stands for BroadCast. The dial markings of 51 to 160 kc are also consistent with this set being made for the American market. John

9th Dec 2009, 12:06 pm	#19
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,960	Re: Grundig 4192 Stereo Radio As a general rule, MW and LW are only marked on consumer equipment in territories where LW is used for broadcasting (Iceland, Europe, Russia, the Middle East and North Africa.) Elsewhere MW is just known as the 'Broadcast Band', abbreviated to BC. I thought BC was used in Australia and NZ too, but I encounter few Australian radios so could well be mistaken. Paul

9th Dec 2009, 9:57 pm	#20
berntd1 Retired Dormant Member Join Date: Dec 2009 Location: Sydney, Australia. Posts: 13	Re: Grundig 4192 Stereo Radio Hello, The radios I have seen, all have MW marked as AM. That is the more moden ones. I don't know how vintage Australian radios were marked. I have seen BC a few times but I seem to remember that it was on some vitage Becker car radios that I used to repair in the past. Kind regards Bernt