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!