Re: Grundig TK 819 Any Useful Info
 

After much searching, today slightly reluctantly ordered a set of 5 Kemet 250vac / 630vdc metallized paper 0.22uF/100 ohms RC snubbers as replacement for the 4 snubbers that have badly leaked.

Would have preferred the higher rating of 275vac in Polypropylene but very difficult to find these for sale and when they are, they are far too expensive due to very large quantity minimum order.

I am sure they have got to be better than the ones that were removed, but probably will not last as long.

Re: Grundig TK 819 Any Useful Info
 

It's interesting that your TK819 has a connector for the mains at all, the one I have I'm pretty sure has a captive mains cord. I wonder if it has to do with requirements for different countries (in my case Sweden vs. the UK).

Re: Grundig TK 819 Any Useful Info
 

Hi Ricard,

Yes that is interesting. The German Service manual shows the mains connector (netzanschluss) and I would say that the part looks original build.

Some of my other old Grundigs (both German and UK) have the mains cable hard wired, i.e. captive.

David

Re: Grundig TK 819 Any Useful Info
 

The snubbers have just arrived, that was quick !

Conversion to 3 pin mini Bulgin mains plug completed. As stated before the plug body (and rear securing nut) was a fraction smaller diameter than the hole left by the removal of the Remote Control socket, so had to make a couple of plastic washer plates.

As can be seen in one of the photos have started replacing some of the paper (dielectric) capacitors, the new ones are the yellow polypropylene ones. Most of the new ones are noticeable physically smaller than the old paper ones, even though the new are higher working voltage (630 vdc).

Bit of a tedious job as some of the capacitors are buried under a birds nest of other components and connections, making some difficult to access/identify. I have made it more tedious by carefully checking the circuitry for each one to the schematic, to ensure I know exactly which ones I am dealing with. Around 10 more to do.

Some of the capacitors are at least double their stated capacitance value, this in itself does not mean they are bad though, but also probably due to their age they will have high leakage currents (yes I know leakage current is normally only referenced for electrolytic capacitors). When I get time sometime out of interest I will check all the removed old capacitors to see if any pass DC voltage/how much.

Found 2 differences from the schematic. Capacitor C11 is shown as a 15nF (15,000pF) but the fitted capacitor is actually 5,000pF (5nF), C11 looks original, I do not think it has been replaced by incorrect value. Looking at the TK 820 schematic, the same capacitor is shown as 5,000pF, i.e the same value as the fitted C11.

Capacitor C24 (0.1uF) is missing altogether, impossible to know if it has always been missing since build or has been removed but not replaced.

Very difficult to work out its operational function without a lot more studying of the schematic. Basically it connects the playback head signal through a switched relay contact out to the Remote Control connector (or maybe the Remote Control connection is actually a input coming in), it also connects to a couple of points in the amplifier electronics.

Most difficult part at the moment is trying to identify which relay controls this particular relay contact. I am not currently going to replace the missing C24, I will look at it in more detail when the unit is powered up and working.

Re: Grundig TK 819 Any Useful Info
 

Forgot to mention the Remote Control socket connector wiring tidy up work, this detailed stuff is mainly for my benefit, as in a couple of weeks or less the fine details may be a bit hazy in my memory :)

As previously thought the link on the schematic across pins 1 & 3 of the connector is the N.C (Normally Closed) switch in the Remote Control connector. So connected together the small red and white wires (i.e. to re-instate the link) that were originally connected to these pins, I actually cut the wires back several inches to make it easier to join them together, also removed the black sleeving the 2 wires were inside.

This link provides +24V to Relay B via various relay contacts.

Screened cable within rigid (due to age) yellow sleeving, originally connected to pin 5, removed completely, note this connected to C24 (yes the same C24 as missing above).

White wire originally connected to pin 4, end insulated with sleeve (other end connects to relay contact).

Re: Grundig TK 819 Any Useful Info
 

Plan going forward:-

1. Continue and complete replacing the old paper capacitors.
2. Clean snubber tar like leak material from the ECC 81 valve base pin holes.
3. Clean snubber tar like leak material from the ECC 81 valve pins.
4. Fit the new snubbers.
5. Refit transport section back onto electrical section and power up, and see what works (may actually first do some power up checks on just the electrical section).

Possible future operational problems may be the very bad condition rubber pressure rollers and the de-composing clutch friction material in the Supply Reel Table (and possibly same in Take Up Reel Table).

Re: Grundig TK 819 Any Useful Info
 

Maybe useful for your collection of mains connector information.

I found this mains cable for sale (in USA) for a Grundig TK 820, looks like it would be the same for the TK 819. Cost would been too high for me to purchase it for my TK 819.

Re: Grundig TK 819 Any Useful Info
 

Thanks. I will add that photo to my reference information.

Al

Re: Grundig TK 819 Any Useful Info
 

Regarding the schematic, the relay contacts that switch the heads are the K relay contacts, but the contacts to the left of C24 (1.12, 2.12 & 3.12) are in the main switch block...12th row...contacts 1, 2 & 3 in the switch layout diagram, contacts 1 & 2 (12th row) connect the output from the rec/playback amplifier to the head when in record and contacts 2 & 3 in the same row connect the output from the rec/playback amplifier to the audio output stage when in playback, pins 5 & 2 on the remote connect the output from the rec/playback amplifier to ground if they are connected together.

Lawrence.

Re: Grundig TK 819 Any Useful Info
 

Hi Lawrence,

Many thanks for that, that is extremely helpful. You obviously can get your head around what I find are confusing relay notations in the Grundig schematics.

David

Re: Grundig TK 819 Any Useful Info
 

No problem, in the switch diagram the position of all the contact wipers are shown when there's no function selected, when a function is selected all the contact wipers for the two column lines for that function move down to the next row of contacts, there's an example shown at the switch diagram of how a circuit ref. for a switch contact relates to it....."Beispel 4,12"

Lawrence.

Re: Grundig TK 819 Any Useful Info
 

Hi Lawrence,

Thank you again, I need to have a study of this to see if it makes sense to me (the brain cells are not as good as they used to be :) ), I am sure that once it does, it will become fairly straight forward.

David

Re: Grundig TK 819 Any Useful Info
 

Ditto.

If you can find relay contact AI in the schematic as implied in the relay contacts table your doing better than me....

Lawrence.

Re: Grundig TK 819 Any Useful Info
 

You have set me a challenge now :)

Could it be the contact to the left of ST II directly below pot R37 ?, the character after the A could be a I but it almost looks like it has got a squiggle through it ?

Re: Grundig TK 819 Any Useful Info
 

I make that one AII, interestingly there's no A2 implied in the TK820 manual, just A1.

Wondering if it's a misprint in the TK819 relay tables.

Must admit some of the relay contact ID's on the schematic are a bit ambiguous although I've managed to figure most of them out.

Lawrence.

Re: Grundig TK 819 Any Useful Info
 

Yes I can see in the TK 820 manual that the same contact is identified as a1 and there is no A2 in the relay table, so agree quite possibly an error in the TK 819 relay table.

The quality of the 819 schematic that I have is not great, but when enlarged the contact to my eyes could be either AI or AII but to me it looks more like AI with a angled line though it.

Re: Grundig TK 819 Any Useful Info
 

Tonight fitted the four new RC snubbers, not very elegant but will do. Cleaned up the horrible snubber tar from the pins of the ECC 81 and its valve holder socket pins, amazing how much gunk came out of the valve holder sockets.

When I eventually get it powered up, if there are any amplifier issues, the first thing I will double check is the ECC 81 in case of any bad contact due to the tar residue.

The 2 internal fuses are loose in their fuse holders due to the sprung fuse holder contacts having lost their springiness, I tried to put some spring/tension back into one of them, but it just fell apart, so will replace all 4 holders.

Replaced a further 3 Frako paper capacitors, this time on the top of the electrical chassis, currently struggling somewhat with a fourth, one end is very difficult to access on the back on one of the front panel push button switches. Managed to unsolder it but struggling to solder a new one at that end without damaging surrounding wires. Have not yet been able to identify which capacitor (C number wise) this is, it is 0.1uF

Re: Grundig TK 819 Any Useful Info
 

C27, the capacitor connected between the push button contacts 1,1 and 2,1 on the switch wiring diagram and the schematic ?

Lawrence.

Re: Grundig TK 819 Any Useful Info
 

I would be a bit wary of those Rifa snubbers - they have a bit of a reputation for spontaneous combustion accompanied by a pervasive pong. I have experienced this a couple of times, granted they were quite old and yours look new. You could make your own with a polypropylene cap of the right value and a much higher voltage and a 100ohm resistor connected in series.

Re: Grundig TK 819 Any Useful Info
 

These are brand new. I think and hope that all the Rifa problems are historic. I did consider making my own, but thought too much effort and too many other things to do.

We will see how they go, hopefully I will not be eating my hat later :)