Help with really old tape recorder

Hi Guys,

I'm trying to repair or even test this really old Geloso StenoTape. It uses a Crystal Mic for an input, which I have, but I doubt is working. Right now I can get it to power up but there doesn't appear to be any output. There is "Some" sound coming from the speaker...

I think I would like to bypass all the tape stuff and test the input/output stages. What would I need to change to make a Line level in or Microphone in work... something other than the dead crystal mic? Also if I need to change anything to drive a regular 8 ohm speaker and or a line input on my Protools rig?

With old machines like this with complex switching, as a first test I would set it to play and try touching the leads from record/play head with an insulated screwdriver. If you get a loud him it is basically working.

Cheers

Ian

ruffrecords said:

With old machines like this with complex switching, as a first test I would set it to play and try touching the leads from record/play head with an insulated screwdriver. If you get a loud him it is basically working.

Cheers

Ian

Click to expand...

Yeah... I tried some of that. I find myself just wanting to feed a test signal through the system, hence the idea of making it receive line level or a regular mic.

> Geloso StenoTape

This thing is HOT CHASSIS!! When you work inside, you are touching one side of the wall-power!!

PLEASE get an isolation transformer.

Yep, it sure is.

PRR said:

> Geloso StenoTape

This thing is HOT CHASSIS!! When you work inside, you are touching one side of the wall-power!!

PLEASE get an isolation transformer.

Click to expand...

Can I feed just a line level from Protools directly into this unit?

Can I ground or modify the chassis in some way to make it safer?

PRR said:

> Geloso StenoTape

This thing is HOT CHASSIS!! When you work inside, you are touching one side of the wall-power!!

Click to expand...

That's reason enough to cut it apart with a bandsaw.

-a

Andy Peters said:

PRR said:

> Geloso StenoTape

This thing is HOT CHASSIS!! When you work inside, you are touching one side of the wall-power!!

Click to expand...

That's reason enough to cut it apart with a bandsaw.

-a

Click to expand...

So True!

I'm finding that it might be possible to wire a grounded ac cord into this and then ground the chassis. Any thoughts on this?

BANG!!!!

As mentioned previously, this is a hot chassis, the chassis is wired directly to the mains plug. If you put the plug in backwards, the chassis is at line volts.

BE VERY CAREFULL, THIS COULD KILL YOU!!

You can make it safe by wiring it to an isolation transformer, and then earthing the chassis.

If you are not sure what you are doing, consult a professional.

radardoug said:

BANG!!!!

As mentioned previously, this is a hot chassis, the chassis is wired directly to the mains plug. If you put the plug in backwards, the chassis is at line volts.

BE VERY CAREFULL, THIS COULD KILL YOU!!

You can make it safe by wiring it to an isolation transformer, and then earthing the chassis.

If you are not sure what you are doing, consult a professional.

Click to expand...

I really appreciate the effort, from all of you!

I have done tons of research now, and all I can say is WOW! That and maybe "Crazy" The sickest thing is there are metal screws that go into the chassis and are quite "touchable" from the outside...

Should I ever "release" this back to a customer without modifying the power?

Hot chassis TV sets were common for many years, so common they even sold "cheater" line cords so technicians could defeat the safety guards that prevented access to hot areas while power was applied.

If it is/was an agency approved design it should be safe for the consumers when buttoned up. An exposed hot screw head does not sound correct, while perhaps in a recessed hole covered by a wood cabinet might be accepted.

I would expect studio customers to blow off any warning safety advice you give them, so use your judgement. Is it a good customer you would miss?  ;D

JR

Got a DMM handy?    When you connect - and do be very careful *NEVER* to touch BOTH chassis at same time - i.e one hand on one and one hand on other when the power is on.

Make your cable connections BEFORE you plug in and power up.  Once powered up, set the DMM to AC volts and put one probe on the tape recorder chassis and the other probe on you DAW interface chassis and report back what the reading was.  After that you may as well reverse the polarity on the two prong tape recorder wall plug and take another voltage measurement.  Theoretically this gives the "across-the heart" voltage.

I wouldn't bother trying to make a recording amp out of this unit.  Save the 12AX7s and the output transformer and maybe the chassis if worth it and start from scratch.  It could very well be less work that way.