Grundig TM45 valve recorder

[krazykatt]

Hi everyone!
I did a dumb thing, and am hoping an expert on here will throw me a bone with some info... I bought a Grundig TM45 valve reel-to-reel from a guy on ebay to use in producing a band that wants a sound like you'd hear on the "Nuggets" 60s punk and garage rock collection. The recorder is a German model with an Euro plug, so I assumed it took 220-240v. I plugged it into a 110-->240 transformer, and it came on, the tape transport worked fine, but I could not get any audio going in or out of it. Then the unit powered off, and I discovered that the transformer was overheated. I bought a pdf service manual for the recorder and realized that it has voltage jumpers on the back, and they were set for 110.
Have I completely destroyed this fine piece of German engineering? The tape transport works fine now at 110v with a simple adapter plug, the tubes light up, but still no audio going in or out.
I may have the audio in/out cabling messed up (it has 5 unlabeled din ports on the back) but before I spend any time translating the manual and trying to troubleshoot that, I'd like to figure out if I need to throw it in the trash and look for another machine or not. This one was really cheap and has a bunch of original-looking Siemens tubes in it, and if I killed them I'm gonna cry...
If anyone can give me a clue what kind of damage 240v going through a 50-year-old recorder set for 110v would likely do, it would be much appreciated.
Thanks,
Ed

[unsolved]

Start measuring the voltages inside, ac and dc. Can you see any fried components?

[gentlevoice]

Any fuses that are blown? Any tubes that don't light up?

Best

Jesper

[Steerpike]

If the tube heaters glow, it shows the transformer primary is still intact - that would have been the most likely thing to have been destroyed.
That is QUITE some transformer that can take an overload like that - I doubt anything modern would survive.

Next to die would have been electrolytic capacitors - but they explode; so you'd KNOW!

Check the DIN cables - they are wired differently for input and output function, if you use the wrong kind of cable - no signal passes.

LOW voltage electrolytics in the signal path may have gone dry, and hence open circuit - but thay would just produce faint, tinny sound, not total silence.

[krazykatt]

Thanks very much for the pointers and the help getting my bearings. The fuses are not blown, there were never any explosions, popping, smoking, etc... and the tube heaters light up. I don't see any scorching or melting inside.

I found a Uher Stereo Record III at a local junk store to use for my project, and it works great, and is very similar. I tried pulling the em84 magic eye tube out of the Grundig where it's heater lights up, but it doesn't come online with the green readout it should produce. When installed in the Uher, it lights up green and displays input level.

At this point, I'm thinking I should get a multimeter and basic electronics repair reference material, and start really learning how to work on this stuff... Its amazing to me that for $50 at a junk store I can get a precision engineered tape recorder full of telefunken and siemens tubes that doubles as a stereo tube mic preamp and amplifier. It sounds amazing with a guitar plugged in, running through the built-in speakers.

[Steerpike]

but it doesn't come online with the green readout

That suggests the high voltage DC supply (called the B+) is dead.
Does this recorder have a selenium rectifier, or a tube rectifier?

Selenium rectifiers dont last long, and usually need to be replaced on vintage equipment. Its a very cheap fix - a silicon bridge and a resistor (resistor to simulate the voltage drop of the inefficient selenium type.)

In many cases you can omit the resistor - you need to replace the rectifier with a silicon one, and then measure the B+ voltage to make sure it's not above that which the electrolytic capacitors can cope with. If it isn't, you're done. Otherwise you need to measure the current and work out the value of resistor.

[krazykatt]

Thanks Steerpike! I'll search the service manual for info about der berichtiger, and see if I can figure out was ist los.

[noah300g]

I also have a TM45, but the main motor appears to be fried.
It was running but then stopped. The motor is quite warm, and can be moved by hand, but not by itself. I have not had any luck figuring out the part number or model number of the motor to try and buy a replacement.
Any suggestions welcome.
thanks,