Grundig 2065 USA model. Can this wiring be correct?

[mpman24]

Hello All:

I'm working on a Grundig 2065 USA model. I've done the usual recitifer replacement and recapping and it is playing quite well, but I noticed these two wires looped together off the UKW switching and don't know what to make of it. The wires are insulated wires that are looped together, not soldered or physically connecting the copper in any way. They appear original (I don't see any evidence that this radio had been worked on prior to me). I believe the wires are "connecting" a coil to the RF can. Can this be correct and, and if so, why would they have done this?


Thanks,

Mark

[Cobaltblue]

Looks as if it might be a "gimmick" capacitor loose coupling or possibly feedback or injection.

Cheers

Mike T

[paulsherwin]

Is it some sort of physical restraint, without an electrical function?

I don't know this model, but 1950s Grundigs are usually very solidly built indeed.

[mpman24]

I agree with the Grundig build quality. I'm a bit of a novice but I've worked on a couple of them and they've all turned out great.

The wire does not look like a restraint of any kind. At first glance it looks like a connecting wire that was cut but on further inspection it seems a bit long for that. If the radio had been worked on previously I would have guessed that someone snipped it but I'm pretty confident that it is original.

What is a "gimmick" capacitor?

[Cobaltblue]

A gimmick capacitor is one where a capacitor made of pieces of insulated wire twisted or wrapped together. Sometimes such as in the case of Philco an insulated wire wrapped around an uninsulated tag.

Cheers

Mike T

[paulsherwin]

Yes, a 'gimmick' capacitor is a low value cap improvised from two bits of hookup wire twisted together. It's quite common to see them in homebrew builds, but you don't see them on commercial designs very often, and I've never seen one in a Grundig.

I wonder if it was something to do with extending FM to 108MHz for the American market. Most European countries only used FM below 100MHz at that time.

[mpman24]

Thanks for all your comments. I appreciate it.

You have much more experience than I do. Would you just leave it as is?

[paulsherwin]

I would leave it alone in the absence of a fault. There may be more expertise on other forums though.

[vidjoman]

It might have been a loop used in the original alignment of the RF stages and for convenience just cut and twisted to make it safe. I suspect that if this is the case then the manual should give a clue in the alignment instructions.

[Radio Wrangler]

VHF/UHF stuff is just where you sometimes need a small capacitance, lower in value than you routinely stock as a component. Gimmick capacitors are also used as low value trimmers. Do not disturb unless you have a solid reason.

David

[ms660]

I don't think it's anything to do with VHF, so far as I can make out if it's a gimmick capacitor it provides a small amount of feedback on AM from the anode of the Mixer to its signal grid via the RF tuned circuit coupling capacitor, but whatever the wires function are/were they're connected between function switch contact 9k and the top/hot end of the MW RF trimmer.

Lawrence.

[mpman24]

I agree with the comments to just leave it alone although it does seem odd to me.

I did find a picture of a Grundig 1060 which appears to be electrically very similar and it looks to have some type of cap that line that also connects over to the SW switch. I find the schematics difficult to understand around the switching points but I do not see any caps at that location on either the 1060 or 2065 model (but I could be missing something).

Thanks to all you commented. I appreciate all your help.

[ms660]

Grundig 2068, same chassis as the 2065.....8 minutes and 10 seconds in:

https://www.youtube.com/watch?v=UtznCOAwN6s

Lawrence.

[mpman24]

Brilliant Lawrence! That shows the exact same wire looping. Will help me sleep tonight knowing that it is how it should be.

Much appreciated!

Mark

[ms660]

Originally Posted by mpman24

I find the schematics difficult to understand around the switching points

It's reasonably straight forward once you grasp the concept.

Referring to the Grundig 2065 schematic, all the contacts in the schematic are identified by a number and a letter, the switch wipers that make the contacts are omitted in the schematic, that makes it easier to visualize which contacts are in circuit for the function selected by referring to the switch diagram, it also enables the wipers to be drawn on the schematic for the selected function with clarity.

The switch diagram at the bottom left corner of the schematic sheet is shown as viewed from underneath the chassis and shows the position of the switch wipers with the functions in the off position, the wipers are the short vertical lines in between the switch column lines, the contacts are the small black dots, the switch columns being numbered 1 to 10, the horizontal rows being lettered from a to l excepting the letter j which is not used, the number and letter shown at the contacts in the schematic corresponding to the number and letter on the switch diagram, eg: in the schematic, contact 5c in the Antenna/RF circuit is shown in the switch diagram where column 5 crosses row c.

When any of the functions apart from Off are selected the wiper in column 1 moves up one position and any wipers in the two columns pertaining to the function selected also move up one position.

Example: When MW is selected the wiper in column 1 will move up one position and contacts 1i and 1k break and the wiper in column 8 will move up and make contacts 8d and 8e, but we can ignore contacts 8d and 8e as they are not used in 2065 version of the chassis.

So how is the MW circuit selected? The answer is it's already selected due to the fact that the other functions (TA, LW and UKW) are not selected, which means that that the wipers pertaining to those functions don't move at all from the positions shown in the switch diagram.

Taking that from the RF through to the AF stages for MW (in order from left to right in the schematic):

First is to bring the MW RF tuning coil into circuit (identified by the figure 2 in a circle) that's done via contact 5b and 5c, the switch diagram shows a wiper making those contacts, next is to connect the RF circuit to the Mixer, that's done via contacts 10b and 10c, the switch diagram shows a wiper making those contacts, next is to connect the Oscillators anode load resistor to the HT line, that's done via contacts 9d and 9e, the switch diagram shows a wiper making those contacts.

Next is to bring the 1st AM IF transformer only into the anode circuit of the Mixer, that's done via contacts 9k and 9l, the switch diagram shows a wiper making those contacts, next is to bring the MW Oscillator coil into circuit (identified by the figure 1 in a circle) that's done via contacts 5i and 5k, the switch diagram shows a wiper making those contacts, next is to connect the AGC line to the IF Amplifier and the Mixer, that's done via contacts 9g and 9h, the switch diagram shows a wiper making those contacts.

Next is to enable the HT line to the Oscillator, the Mixer and the Tuning Indicator, that's done via contacts 4k and 4l, the switch diagram shows a wiper making those contacts, next is to select the output from the AM Detector, that's done via contacts 10g and 10h, the switch diagram shows a wiper making those contacts, next is to disable any effect the FM discriminator might have on the AGC line, that's done by contacts 10k and 10l, the switch diagram shows a wiper making those contacts, next is to route the output from the AM Detector through to the AF Amplifier, that's done via contacts 3k and 3l, the switch diagram shows a wiper making those contacts.

If that's any help.

Any errors then guilty as charged.

Lawrence.

[mpman24]

Thanks, Lawrence. I'll work my way through your example and am sure it will be a help.

Out of curiosity, would the twisted wire that started this thread be shown on the schematic?

[ms660]

Originally Posted by mpman24

Out of curiosity, would the twisted wire that started this thread be shown on the schematic?

They're not shown in the 2065 schematic that I have so far as I can see, they could have been fitted as a gimmick capacitor or as test points for factory alignment/checks.

Lawrence.