Restoring my Telefunken Opus 7 - some pointers welcome

[radix39]

Alright, I took some time today to finally disconnect the speaker wires so I could remove the chassis. The underside certainly looks frightening, to say the least:



There is just an insane number of resistors and caps under there. Probably the main reason these sets sound so good. Its probably not the best radio for me to work on as my first, but I think I can get it working great again.

I started making a long list, writing down each of the caps that I come across and their values - especially the paper caps. There are a few buried deep under a ton of wire that i'm not sure how i'm going to get at. The wires are old and brittle, and i've already had one just randomly snap on me as I tried to bend it out of the way to get a better look at a cap's rating.

I also came across a large black can. I assumed that it was the filter capacitor, but after undoing the hinges so I could turn it around and read the specs, it seems to be something else - a rectifier?



Is there anything I need to do with this, or just leave it alone?

Once i'm done mapping, i'll drop over to a local shop and pick up the replacements that I need, and start replacing them one by one.

[jeffsod]

Make sure you take a lot of large file photos detailing the underside of the chassis. I am pretty sure you need to pay close attention to the position of the cap you are replacing.

The tech I know has a fantastic setup for working on these. Essentially looks like a captial H with the chassis the bridge between the two columns mounted constructed with plywood and rotatable. The chassis is mounted to the columns. Somewhere I came across somthing similar that you could purchase online but you could build something similar if you wanted.

Either way take it slow and be careful around those angel hair wires!

Edit-
Heres a chassis cradle sold by Steve Strong of the Oklahoma Vintage Radio Club. It says he offers two sizes; small $37.50 & large 55.00 plus shipping. Email scstrong1@cox.net
No affiliation but thought it might be helpful if you don't want to construct your own.

[Josef]

Hello!

Originally Posted by radix39

Alright, I took some time today to finally
...I also came across a large black can. I assumed that it was the filter capacitor, but after undoing the hinges so I could turn it around and read the specs, it seems to be something else - a rectifier?
...

Yes, you are right-this is a rectifier. I'm going to translate the words printed on the can:
Gleichrichter> rectifier
Blau> blue
Rot> red
In this radio it is also not usefull to replace all the caps. The smaller valued silver coloured caps are usually very reliable. Only replace the black caps.
The EL 84 is a very common and extremely reliable tube. It is used in my daily player and it works well since decades
Greetings Josef

[radix39]

Wow its been a while since i've been in this thread. I thought I would just update all of you.

I finally got around to picking up the caps I needed for this project. I worked on it last night. I replaced 1-2 caps at a time and then plugged it in to make sure I didn't screw something up. So far so good. I replaced the filter caps on the top of the chassis as well as an electrolytic and some other paper caps next to the speaker output terminals. The sound so far is much improved! The constant hum is gone and the overall volume is much, MUCH louder. There is actually some decent bass response now. I can also now hear the tweeters working - something I couldn't hear before even with my ears right up to them.

The "farty" sound on FM when warmed up is still slightly there but I still have a good amount of caps to change still. I did have a couple of questions though.

1.) I was unable to find one electrolytic cap in the proper value, but I did find the proper value in non-electrolytic cap. Is it ok to substitute a non-electrolytic in its place?

2.) One of the EL84 tubes seems to be running very hot. Its the one closest to the rear of the unit by the AC line cord. The other one runs no where near as hot. If I switch them around, the heat remains coming out of the same socket, so its not related to that specific tube. Is this normal? The other tubes doesn't seem to generate anywhere close to that amount of heat.

3.) For the 2 50uf caps in the can, I assume that the negatives go to the ground (chassis) and the positives go to their respective leads?