RE-301 Erase Head Issue (Solved!)

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inputhone

Well-known member
Joined
Aug 17, 2010
Messages
53
Hey there,

i just found an old post within the Lab about a damaged bias coil within a roland re 201 echo. I am currently repairing a 301 and i have solved a lot of things (like not working chorus, s on s, reverb) but my erasing head isn't working properly. it always leaves something on the tape.

from the shematics i dont get how to check the 70v at 60khz to see if the head gets enough voltage. unfortunately i don't have my scope around.

anyone any suggestions? i messured the resistance of the coil (incircuit) and it gives me something like 4,5ohm and 0,5ohm (almost 9:1) which is okay i guess?

would appreciate any help  :)
 
First, make sure that the 'sound on sound' "feature" is disengaged. Been there...

How loud is the playback after it has traveled past the erase head? Is it close to the original playback level or is it much quieter?

Have you done the calibration procedure described in the service manual?
 
the sound on sound is - of course - set to off. the sound that is left on the tape is really quiet, so it is just not erased fully but a bit. the signal from the playback heads seems to be good and loud enough. its really just that there is some quiet signal left on the tape. the tape is a new one as well.

i haven't done the electrical calibration (but the mechanical) as i don't have a scope, which i guess is needed for some of the tasks. or is there a way to go without a scope?

would be happy about a step by step advice if anyone would mind :)?
 
SoS off. Good. Just checking...  ;)

Step by step? No. But:

Most of the electrical adjustments can be done with a volt meter and your ear. Read about basic tape machine alignment and get creative. A tone generator and o-scope are highly recommended, though.

The mechanical setup of the Space Echos has a large effect on how well the tape records, plays back and erases signals. I find that without a rock solid mechanical alignment, the electrical stuff is better off left alone. Even when I have done more major repairs on these, most stuff gets checked, and then left alone.

I think that you'll find that you can get better performance from the erase head by varying the height/angles of it. The mechanical alignment is not quite 'set and forget'. More of a slow refining if you ask me.

That being said, there is a balance you'll want to strike between performance and the wear you will put on the heads. Don't go crazy changing things too far from where they probably should be.

Unless you know where to find some new heads.

Which you probably don't.

At least *I* don't.

Play around with azimuth, height, etc. A little tinkering won't hurt. Assuming you don't have something silly like 456 on there. Which I'm assuming you don't.

Grab a screwdriver, play some tones/noise through it and see what you can come up with.
 
You could use a volt meter.

However, without better test gear, the precise level is not critical to achieving acceptable results.

As a rough start, once preliminary mechanical adjustment is made, disconnect the record and erase heads, and remove the tape loop. Make a loop of, say, 10khz on a tape machine which is properly aligned. Put that loop on the Space Echo and adjust each playback head's height/azimuth/etc. for greatest level. Now connect the record and erase heads. Play a 10k tone into the unit. Monitor one of the playback heads and adjust the record head for greatest level. Remove the tone from the input and adjust the erase head for best erasure.

This procedure is, at best, acceptable. It will 'get you through the gig' as they say. Better would be to have some test gear, and best would be to find someone with experience aligning tape machines, better still, Space Echos. The heads won't last forever, and with improper alignment, they'll go bad much quicker. If you don't know what you're doing, find someone who does. Otherwise you'll have a very cool looking, very useless Space Echo on the shelf.

Edited (like always) for clarity.
 
I hope I don't sound like a jerk for all the warnings about the heads. Sounding like a jerk for other reasons, I'm ok with.

I really am trying to help, I've just seen too many badly aligned and almost ruined Space Echos. Be careful.
 
no sounds great. i repaired a few of them before, but never had to actually recalibrate them, as it was more about the electronics. so what you reached is that i am getting a new scope now (old is not working anymore), and will be doing that. hope i can ask some questions when it comes to it..

thanks!  :)
 
I don't have tons of experience with space echos but fixed ours the other day and the number one thing that effected its performance was the tape tension, check the little sprong felt pad before the tape feeds onto the heads. The erase heads first i think?
Also found re-lubing the motor baring helped. You can buy new ones on ebay for £10
Oh and all of what Dreams said...

 
mmm do you have a link to show us these motors on ebay ?
i have a few space echos that needs  restoration....
regards,
Francois
 
I ment you can buy the motor bearings for £10 not the whole motor, they're unobtainaum. But the original motors can take alot of abuse.
Heres a how to link
http://www.hillscloud.com/2011/06/roland-space-echo-motor-rebuild/
 
Dreams said:
You could use a volt meter.

even with a scope how to obtain 3,8mV thats really little. is it meant as rms? my scope cant show that, neither can my multimeter. but maybe it is due to my sound device? i create square wave signal in my mac and send it out through my rme. wenn i com down to 20 mV it already gets really muddy, no way to see clear and the squarewave itself that i produce does not look to good. any help?
 
when i prdoduce square with my sh101 from roland i get nice square shapes on the scope. think there is some kind of self-osciallation going on with my rme.

but still i dont understand how to obtain 3.8mV at 1kHz as this is really low signal. i cant read that anymore on my scope and my multimeter also says goodbye. so how can i reach that signal as asked for in the specs?
 
not to jack the thread but  got a re-301 that does not echo. It will perform all the rest, sound on sound, reverb,chorus but does not work in echo mode. Any suggestions? unit was recapped not too long ago and echo worked for a minute then slowly started to crackle and die out and now doesn't echo at all but as stated before the rest of the functions work without any issues.
 
pucho812 said:
not to jack the thread but  got a re-301 that does not echo. It will perform all the rest, sound on sound, reverb,chorus but does not work in echo mode. Any suggestions? unit was recapped not too long ago and echo worked for a minute then slowly started to crackle and die out and now doesn't echo at all but as stated before the rest of the functions work without any issues.

first check if all heads are not working (by reading the manual you can skip through the heads and combinations by the modeselektor) and check all connectors. as the s on s works you have probably something after the tapehead transistors. check q26 if still working and ic13a. there got to be something wrong within this area of the circuit..
 
> how to obtain 3.8mV

1 Volt. 27K. 100 ohms. Ground.

This gives a 100/27,100 voltage divider. Output is 0.00369V or 3.7mV.

If you can read 1V with good accuracy, and use 10% or better resistors, this will come out right.
 
What he said.

If I remember correctly, there was some funny business with the output jacks and the echo signal. Some sort of "normalization" kinda thing. I had some problem where the solution turned out to be that a tab wasn't making contact with something else it was supposed to be contacting. It may have been crud/dirt/oxidation, or it may have been that yellow goop stuff that Roland used, but either way. I think I even pulled apart the jack to fix it.

Futz around with the output jacks and see if you can get the echo signal to come through. It may be worth it to just remove the jacks and give em a good deoxiting (if I may make up a word) wherever metal touches (or is supposed to touch) metal. Never a bad idea if you got the time.
 
Dreams said:
Have you done the calibration procedure described in the service manual?

hey, i checked it, got a new function generator and took out my old scope from the basement. i tried to calibrate but failed cause the erase head is actually not fed with enough voltage. i measured and found the following things out.

(shematic again: http://funkstudio-berlin.de/coil.tiff)

the broken unit provides the -13,26V after R415.

and keeps it almost after R414 where it is -13,03V. so everything's cool there as with a working unit. also at the transistor's emitter.

after the transistors (collector) i measure (with my scope) approx. 15Vpp instead of approx. 24Vpp compared with a working unit. and also at the coil input.

after the coil i measure falsely approx. 116-120Vpp instead of the approx. 180 Vpp compared with a working unit.

also: the recording head is set to the right voltage with the vr19 also compared to a working unit and records fine. the erase head is not erasing - still.

any ideas? i first thought it might be the transistors but in-circuit check came out almost fine. was good except for collector to emitter said 0,6V instead of 0,57V but that is still in the range i guess. and no shorts there.

the coil also seemed to be fine as it had the same ohm on each wiring as with the working unit (first wiring6,4ohm; second 0,4ohm; also in-circuit). what can it be? something around the transistor area? maybe the caps?

what would you say could be the problem, i ran out of ideas..
thanks a lot folks, please help!



 

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