Dynacord Echocord Super 61 tube tape echo replacement playback head

[beatnik]

I am trying to restore an old Dynacord Echocord model Super 61

I have starting with the more straight forward jobs like replacing capacitors and drifted resistors

The motor spins around and mechanical function is ok, i replaced some of the rollers

Unfortunately one of the two playback heads is open and needs to be replaced

I have tried searching on ebay but no luck.

JRF Magnetics is the only supplier of magnetic heads that I am aware of and I have had a quick look at their catalog, but I am unsure what would be a suitable replacement

The working playback head I have measures about 1K ohm on the multimeter, isolated from the circuit. The three recording heads measure 430 ohm and they are all fine

Some readings I have found on another website and seem to confirm at least my resistance measurements. I ignore how to perform the other measurements they done

The 3 recordingheads
**************************
Resistance: DC=448 ohm, 120Hz=1090 ohm. 1Khz=16,7 Kohm
Inductance: 120Hz=719mH, 1Khz=636mH, Q=3,9 D=0,256 (at 1Khz)
Capacitance: 1Khz=38,47 nF

The 2 playbackheads
*************************
Resistance: DC=1019 ohm, 120Hz=3,73 Kohm, 1Khz=43Kohm
Inductance: 120Hz=2,26H, 1Khz=1,81H, Q=3,46 D=0,288 (at 1Khz)
Capacitance: 1Khz=12,68 nF

This is the JRF catalog page for 1/4" full track width mono heads, model PR-B1F. There are a few different types available, but it seems to me the resistance values are all much lower than what my Dynacord head is measuring, so I am unsure there is actually a suitable replacement, I have tried emailing JRF but no reply yet.

http://jrfmagnetics.com/Nortronics_pro/nortronics_silver/pdfs/p26.pdf

It would be great to understand how to select a correct replacement head as it would be also useful for possible future repairs

 

[API]

Are you sure there are three recording heads?
Normally a tape echo have one recording head, three playback heads and one erase head.

 

[beatnik]

yes i am sure, also they are listed on the service diagram (model  Super 62 which is pretty much the same)

https://www.dropbox.com/s/k3l09xtjjyeyf1w/Dynacord%20Echocord%20Super%2062%20full%20service%20manual%20%2876-103%29.pdf?dl=0

attached is the schematic for the Super 61 that I have

 

[panman]

Try this: http://bobbysreparaturen.de/

 

[beatnik]

thanks, i'll send an email

 

[DerEber]

Bobby is the man!
He did my ng51 too.

 

[abbey road d enfer]

It would be great to understand how to select a correct replacement head as it would be also useful for possible future repairs

Vacuum tube electronics require high-Z playback heads. All the heads on the page are for solid-state usage.The heads that are most likely to work well with your Dynacord are models 7410/7411 in Professional heads. Now, I don't know if they are mechanically compatible.

 

[API]

That is pretty cool with the three recording heads, i have had many of these echos but never knew that!
I guess it records the signal three times on the tape and then the playback heads play the three recordings x2 for the repeats?

 

[PRR]

> models 7410/7411

http://www.jrfmagnetics.com/Nortronics_pro/magheadspecs/Nortronics%20Pro%20Magnetic%20Head%20Specifications.pdf

http://www.shop.ballardsupply.com/TAPE-HEADS_c57.htm  <-- $14-$16

These are designated as Play heads. Are they suited for the record head function? (I know they can be.)

 

[abbey road d enfer]

These are designated as Play heads. Are they suited for the record head function? (I know they can be.)

From the OP: "Unfortunately one of the two playback heads is open and needs to be replaced"

 

[beatnik]

JRF got back to me and they suggested model GMH2L-N7 . That one can't be found on the catalog but they told me its specifications are as following

Mono 1/2-track (.080 track width) centered on 1/4-inch tape,
800mHy inductance,
500 ohm DCR,
100 micro-inch gap

The price they quoted me is much higher than the Nortronics 7410 / 7411 available in that shop (thanks PRR), so I am really towards following your suggestion, as long as the different specifications are not an issue.

The 7410 has a higher dc resistance than the head JRF is offering, and also higher than the original Dynacord head. Is that going to be an issue ?

Gap on the 7410 is wider, but probably hf response will be good enough for a guitar device ?

The JRF head comes with threaded holes to fit the Dynacord mounting plate, but i have seen the Nortronics has an optional mounting bracket which can probably fit

 

[Noth]

Hi,
I know that's a pretty old thread, but for the record..

I own a Super62 which had two of the three record heads "dead" (ie. cut).
I opened up the two and was able create one working head from these.
Inside each head, there's actually two coils and when a head is "cut", usually only one of the two is dead.
So, the trick is to unsolder the very thin wire between the two coil (as thin as a hair, so you will need a microscope) then test both coils.
Now, do the same with the second head and create a new one with the two working coils.

It will require much patience, solder flux, a very sharp blade, some soldering skills and hot glue to rebuild everying back into place.

 

[abbey road d enfer]

Super job!

 

[havazli]

Hi,
I know that's a pretty old thread, but for the record..

I own a Super62 which had two of the three record heads "dead" (ie. cut).
I opened up the two and was able create one working head from these.
Inside each head, there's actually two coils and when a head is "cut", usually only one of the two is dead.
So, the trick is to unsolder the very thin wire between the two coil (as thin as a hair, so you will need a microscope) then test both coils.
Now, do the same with the second head and create a new one with the two working coils.

It will require much patience, solder flux, a very sharp blade, some soldering skills and hot glue to rebuild everying back into place.

Would you like to tel me how did you get the tape head coil out of the can? Did you heat it?
Thank you?

 

[Noth]

Would you like to tel me how did you get the tape head coil out of the can? Did you heat it?
Thank you?

Hi,

As far as I can remember, I just did unscrew the two little screws at the bottom and that was it.
It was quite tedious to extract the coil from the case because of the cable that goes through the back hole.

Actually I stopped working on those, my fixed tape head, and all the others that were working fine, did actually also burn soon after
I guess there was some issue with the circuit and too much current was sent though the heads but I can't figure out why/how..