Grundig 3028 WZE

[jrsroadhauze]

Just purchased this fine old radio. When you power it up it has a loud hum. Any ideas would be great.

['LIVEWIRE?']

First suspects would be things like the reservoir & smoothing capacitors, and possibly the rectifier, especially if the latter is a selenium type.

[jrsroadhauze]

Thanks for the quick response. Im a retired stationery engineer so electronics are new to me. Sorry what are the reservoirs? The rectifier, would that be the EL 95 tube

[cathoderay57]

Not sure how deep you want to go but if you want to do a decent job to preserve this radio and keep it operating reliably for a few years at least, there is excellent guidance here: https://www.vintage-radio.com/repair...and-tests.html . I've found that Grundigs from the early '50s tend to have very leaky paper capacitors (even though they are not usually the older "waxy" type) and most need replacing. If nothing else, do as Livewire suggests and also replace the paper coupling capacitor between the anode of the EABC80 (pin 9 clockwise viewed from underneath) and grid of the EL84 ( pin 7 clockwise viewed from underneath)

[paulsherwin]

European tubes use a systematic naming convention which allows you to easily work out their function. See https://en.wikipedia.org/wiki/Mullar...be_designation

An EL95 is a 6.3V heater output pentode on a B7G 7 pin base.

[cathoderay57]

Apologies, I was looking at details of the Grundig 3028 which has a different valve (tube) line-up to your WZE model. The principle of my comment still holds good though - the capacitor connected to grid 1 of the EL95 should be replaced. It looks like your set doesn't have a tube rectifier - as Livewire said it is probably a selenium type. In view of your newness to electronics I would recommend you try to find some local help with this, although if you are really keen to learn there are definitely people on this Forum who would probably be happy to talk you through the procedures. Cheers, Jerry

[Cobaltblue]

Hi JRZ

I can't find an exact match to your set but this may be quite close so worth having a look at.

https://www.radiomuseum.org/r/grundi...037_wze3d.html

If its close enough (look at the positions and types of the tubes for example) it will give us a starting point.

I am no expert of these post war Grundig sets for sure but its possible the WZE refers to the sets ability to run from 110V line or a 6V supply via a Vibrator.

A Grundig expert may know for sure

Cheers

Mike T

[paulsherwin]

It's likely to be an export set for the US market. Some of these didn't have a direct UK/European equivalent (the US models all tuned to 108MHz for one thing).

[Techman]

I can pretty much tell you exactly what's wrong with your radio. It's as has already been mentioned, which is the smoothing can. This is a double electrolytic capacitor in one aluminium can. It's the cylindrical silver thing located under the chassis on the far right hand side as you look from the rear of the set. You'll probably notice some dried up corrosion which has leaked from the middle of the black rubber end where the two electrical connections are located. One or both of the internal capacitors will have gone open circuit. You can either try to find a direct replacement of similar values and working voltage or fit two separate replacements, but the first one immediately electrically following the rectifier will have to be a special one with appropriate ripple rating, otherwise it won't have such a long life as the original one has had.

Some folk are quite obsessive about replacing the original selenium rectifier which is the round black thing near by, but I personally only replace these if they're faulty, which I find isn't very often.

Having replaced the smoothing can capacitor/s and found that there is still a bad hum, then it's possible that the rectifier has reverse leakage and needs replacing after all, but this is unlikely.

If you then have a relatively hum free radio, don't carry on running the set for any length of time as the other capacitors advised by others will need replacing before they cause major damage to the set. I seem to remember that there's around four critical capacitors of this type that are all around the audio amplifier and output stage.

[cathoderay57]

From pics on the Web the WZE variant (1958) covers MW + 4SW bands. Valve line-up ECH81, EF89, EBF80, EL95, EM80/81 magic eye + B250C75 N2 selenium bridge rectifier, which according the RadioMuseum was made by AEG and housed in a tall black can, in appearance much akin to a screw-type aluminium can capacitor with 4 wires. Couldn't find a circuit though. Mains 110-240v and facility to plug in a vibrator power pack. Cheers, Jerry

[Techman]

From what you say, Jerry, it sounds like the set in question is a quite a bit different from the 3028 with VHF/FM and an EL84 output valve that we all know so well. However, it also sounds as though the basic component layout under the chassis is very much the same. I've got a feeling that the OP was thinking that this would just be a simple case of pulling a faulty tube (valve, as we call them here) and just plugging in another. Sorry, but there's a lot more to it than that and if he wants to get this set working properly, then there's some learning and some not inconsiderable work to do first!

[jrsroadhauze]

Thank you for all the help will post some pictures when I can.

[cathoderay57]

Here's the link I found, with decent images https://inlandempire.craigslist.org/...010363176.html Odd that they went to the expense of fitting 3 speakers in an all-AM set!

[jrsroadhauze]

Yes that is the one I purchased for $75.00