space echo repair....no echo!

[bmac]

hi there..just wondering if there is an easy solution to this that I can do myself..my RE 301 was working fine, then chewed the tape..when I replaced the tape the delay signal was suddenly absent..what could cause this? could the heads have become magnetized? would that render them useless until demagnetized? thanks!

[Mark Black]

Easiest solution - perhaps the tape is reversed (wrong side towards the heads)?

[Enzo]

Right.

ANd your heads would not magically magnetize in an instant. Magnetized heads lose high end recording response, they don't go dead. They just get sorta muffled.

[bmac]

Right.

ANd your heads would not magically magnetize in an instant. Magnetized heads lose high end recording response, they don't go dead. They just get sorta muffled.

well, i've tried a few different types of tape, and tried them on both sides, no sound..strange..just immediately stopped working.

[Enzo]

Well, if it ain't the tape, it is something in the electronics. I'd look for loose wires, I'd touch the playback head wirs to see if hum comes out - checks the playback amp. I'd be looking for a lack of bias oscillator.

[bmac]

Well, if it ain't the tape, it is something in the electronics. I'd look for loose wires, I'd touch the playback head wirs to see if hum comes out - checks the playback amp. I'd be looking for a lack of bias oscillator.

thanks enzo..the funny thing is, it IS playing some of the previously recorded stuff on the tape I just put on it..little scraps of sound are looping sparsely..it doesn't seem to be recording..

[Enzo]

That points right at the bias oscillator then. No bias - won't record.

[Bernardduur]

How to check the oscillator bias?

I have the same problem......... older 501........ don't know if it ever worked but I scored it very cheap. No reverb and no delay. The reverb was easily fixed as the reverb tank was busted.......... but no delay yet. I replaced all caps in the audio path (as they looked pretty busted) but yet, no avial. Also checked the IC's (by replaing em) and the NE570 but no signal. When I audio probe the heads I get a clear signal on the recording head (although a tad highish with less output). When I turn the bias oscillator trimpot the delay gets there but it is very little, no repeats and the sound is really low. When the bias trim is set otherwise I get no delay at all!

When I scope it I get signal until the bias trap, there the oscillator and overpowers the input signal. The oscillator signal is clear sinal but HUGE (can't read the specifics of the signal because my scope isn't tested)........

Any ideas where to continue? I replaced the oscillator ELCO cap last night as it was busted. Dunno, but maybe the transistors there are also busted? Will also replace the other caps there.

[Brad1]

Just wondering. What do you suppose caused the tape to jam in the first place? Does the transport path seem to be functioning fine, and is it all clean? Did the jammed tape maybe knock something askew? Did something go askew and jam the tape?

See what I'm getting at here?

Unit working fine. Unit jams tape. Tape jam = mechanical cause. Installed new tape. Doesn't work properly. Malfunction could be mechanical or electronic. Which would I most suspect?

If the timing belt went out in my truck, I'd replace it. If the truck doesn't run after I replaced it, I wouldn't suspect an electronic malfunction. I'd suspect something that had to do with the timing belt. Either something internal of the engine caused it, and even a new timing belt wouldn't work...or, I installed it incorrectly.

The first thing I would be looking at is the entire tape path to make sure everything is moving smoothly, and contacting properly. Hard to imagine an electronic problem happening at the exact same time as a mechanical one.

Just a thought.

Brad1

[Bernardduur]

I had the same thought!

Will start a new thread to discuss my problem so we can zoom in on one problem at the time!

[Ted]

When I scope it I get signal until the bias trap, there the oscillator and overpowers the input signal. The oscillator signal is clear sinal but HUGE (can't read the specifics of the signal because my scope isn't tested)........

Funny you should mention this, I've got an RE-201 here with no echo - similar symptoms. Single clean and matching levels until the bias trap where thesignal is overwhelmed. Ah... the signal at the collector of Q4 (final audio transistor) is shown as being completely clean in the manual. I'm seeing bias frequency on it. Suppose that the bias frequency had drifted away from the trap frequency...

[km6xz]

Brad used logic that is the way a tech would approach the problem. The most recent change preceding a change in operation is a pretty good odds bet.
Did you use a real Roland tape or did you make your own from 1/4" reel tape? If the latter, was it older tape that possibly had hydroscopic binder like Ampex 456.
If so, you might have simply clogged the repro or record heads. After a while the tape might start dragging and squeaking if it older tape that has absorbed moisture into the binder. If that is the case, you can bake the tape in a convection or electric oven at about 135F for a a couple hours to rescue it.
If the erase head is clogged, old recordings will be heard, usually with varying muffed sound. If the tape was a Roland tape, are you sure it was an original because they have not been made for over 1/2 decade?
The tape stock is not like reel to reel tape, it is cart tape.
You can verify if the repro heads and amp is working by bringing a wall wart transformer near the head with the unit working. The field from the transformer will induce a strong 60hz signal.

As a first step; Clean the heads with alcohol and firm Q-Tip.

[Ted]

Finally solved the problem. It was the tape tension. The pinch roller at the back must be properly adjusted to pull the tape through. At the front there is a pad on a piece of flat spring which tensions the tape. If pad on it is clogged with oxide, or the spring tension has changed, there is insufficient tension to hold the tape against the heads.

There's a service manual out there somewhere which explains how to do it using spring balances and stuff. I just nudged the adjustment in until it worked...