space echo hell

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twiitala
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Re: space echo hell

Post by twiitala » Thu Jan 29, 2015 6:51 pm

Thanks for the reply Darlington Pair!

Actually, the meter doesn't operate at all. I have a dry signal, but the reverb does work as well.

I'll have to double check the values with the placement diagram, but I'm pretty sure I did it correctly since I replaced them one by one.

I very well may have disconnected or bridged something.

Do you happen to know if the jumper wire between the two resistors on the bottom of the echo board is between R50 and R35? I've attached some photos. I circled the resistors and then put a pencil mark where they're jumpered. I might have misplaced one end of it?.

I've checked all the inputs and they each do the same thing. The tape has the more brown side down.

I have an audio probe. Q8 on the power supply board just gives me the sound of the motor. On the echo board at TR8 I have a faint signal on the middle pin. I'm not hearing anything on the record head. Should I be getting a voltage at the erase head? It doesn't seem right, but there's continuity between 54 on the power supply board and ground. Which looks like it's coming from the pins on V21.


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Thanks again!
Darlington Pair wrote:If you crank the intensity all the way up does the meter move from self oscillation and you just aren't hearing it at the output?

I hate to say this, but grab the parts placement diagram and make sure you didn't accidentally put a wrong value cap on a transistor gain stage because it could seriously effect the gain. Hopefully there isn't something that didn't accidentally get disconnected or a solder bridge when you changed the caps, but we've all done it.

Also, just in case, did you check all of the inputs including the from PA? The Echo/Normal switch could be an issue. I also hate to say this, but make sure the magnetic side of the tape is facing the right way, I've seen them where someone got turned around while splicing and spliced the wrong side.

Do you have a scope or an audio probe? You're going to need one of either if we get to the finding where audio disappears.

Am I right in assuming that you have a dry signal? Maybe your problem is around Q7 or Q8. If you have a scope you can look for signal at the record head to see if your problem is pre or post tape.
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Darlington Pair
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Post by Darlington Pair » Fri Jan 30, 2015 12:09 pm

Ok, the fact that your reverb works says that jumper is in the right place, it jumps from input amps to the reverb stage on the schematic.

Q8 is make up gain before the output stage/mixer, you should have wet audio there (I'm not sure you'd hear motor noise there, it's probably power supply ripple, but there are several places the motor can induce noise in wires, I put clamp on ferrite chokes on all of mine and the noise cleared up). 54 shorted to ground is not good, but it just may look like it's shorted because of L23, the coil is a small resistance to ground, look at the voltage there, if it's zero then it's an actual short to ground an my guess is a shorted C103.

If you really want to clean this thing up from hum when you get it working then through the biggest caps you can find that will fit for C108, 109, and 110 it's the capacitance multiplier circuit for the audio amps. Hiss can be taken care of by replacing the audio transistors with modern more low noise ones. I also replaced any 1uF coupling caps with film that are in the audio path and any of the larger audio coupling electrolytics got replaced and bypassed with high quality film caps. Once all the noise is gone the tape goodness really shines through. Also, doing the Billy Zoom input mod really helps with the miserably low impedance/nasty bandpass filter on the input. I started there but then used the RG Keen mods to the Jack Orman Mini-Booster as my input stage.

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Re: space echo hell

Post by twiitala » Fri Jan 30, 2015 7:24 pm

Cool. Glad to know I put the jumper back in the correct place.

So you're referring to the Q8 on the echo board? I heard the "motor" on Q8 of the power supply board. It's right by one of the multi-pin connectors for the motor. When I checked Q8 on the echo board, I only heard a faint signal on the middle pin of Q8. I'll have to check them both again to confirm.

Right now without the delay working there's a lot less hiss than before. I'll have to see what the noise level is like with the delay working. I'm sure I'll swap out more components once the delay issue is sorted. The mods sound interesting as well.

I'm not sure why anything would have happened to the area around 54, L23, C103, etc. on the power supply board since I didn't replace anything on that side. I'll check for voltages there and let you know what I find.

I do notice that when I'm checking other places on the power supply board that I'm having issues finding a proper ground. At least I think that's the problem. Sometimes when I check the voltages on 61 and 62 I get negative voltages and then I check them again and they're positive. Also, the voltage for the motor doesn't always register on my meter. Really strange.

Well I'll let you know what I find out tomorrow and get back to you.

Thanks!

Trevor

Darlington Pair wrote:Ok, the fact that your reverb works says that jumper is in the right place, it jumps from input amps to the reverb stage on the schematic.

Q8 is make up gain before the output stage/mixer, you should have wet audio there (I'm not sure you'd hear motor noise there, it's probably power supply ripple, but there are several places the motor can induce noise in wires, I put clamp on ferrite chokes on all of mine and the noise cleared up). 54 shorted to ground is not good, but it just may look like it's shorted because of L23, the coil is a small resistance to ground, look at the voltage there, if it's zero then it's an actual short to ground an my guess is a shorted C103.

If you really want to clean this thing up from hum when you get it working then through the biggest caps you can find that will fit for C108, 109, and 110 it's the capacitance multiplier circuit for the audio amps. Hiss can be taken care of by replacing the audio transistors with modern more low noise ones. I also replaced any 1uF coupling caps with film that are in the audio path and any of the larger audio coupling electrolytics got replaced and bypassed with high quality film caps. Once all the noise is gone the tape goodness really shines through. Also, doing the Billy Zoom input mod really helps with the miserably low impedance/nasty bandpass filter on the input. I started there but then used the RG Keen mods to the Jack Orman Mini-Booster as my input stage.

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Post by Darlington Pair » Fri Feb 06, 2015 11:29 am

Yeah, Q8 on the echo board, I think where you're talking about is actually part of the motor control circuit of the last power supply board version, you had me confused for a while because mine only has one Q8.

Q9 is the output buffer right before the attenuator switch, it's working because you have dry signal. Make sure C70 is 47uF and not 4.7uF and make sure your eq pots are clean, check for bad solders around Q8, signal at the collector of Q8 is a good thing, you might not have enough gain or R86 is open somehow. Although you should have signal at pin 1 and bigger signal at pin 2. You can replace this with a 2N5089, but you'll have to bend legs.

The last solder lug opposite the end of the supply board with molex connectors is ground on both sides of the board.

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Post by twiitala » Tue Feb 10, 2015 8:32 am

Thanks for clarifying where Q8 is.

I'll check to make sure C70 is 47uf and R86.

I've been slacking on this?.I'll be in touch soon.



Darlington Pair wrote:Yeah, Q8 on the echo board, I think where you're talking about is actually part of the motor control circuit of the last power supply board version, you had me confused for a while because mine only has one Q8.

Q9 is the output buffer right before the attenuator switch, it's working because you have dry signal. Make sure C70 is 47uF and not 4.7uF and make sure your eq pots are clean, check for bad solders around Q8, signal at the collector of Q8 is a good thing, you might not have enough gain or R86 is open somehow. Although you should have signal at pin 1 and bigger signal at pin 2. You can replace this with a 2N5089, but you'll have to bend legs.

The last solder lug opposite the end of the supply board with molex connectors is ground on both sides of the board.

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Re: space echo hell

Post by twiitala » Tue Feb 24, 2015 6:41 am

So I've been meaning to post an update for a couple of days.....

I've got things mostly working with the delay now......
I found a tiny solder ball that was shorting out one end of a cap on the echo board. So now everything works except for the repeat rate function. I'm going to check the power supply pcb and see if I missed another solder ball somewhere.

I feel like an idiot but at least I'm getting somewhere. Haha.

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Re: space echo hell

Post by Darlington Pair » Tue Feb 24, 2015 2:13 pm

twiitala wrote:So I've been meaning to post an update for a couple of days.....

I've got things mostly working with the delay now......
I found a tiny solder ball that was shorting out one end of a cap on the echo board. So now everything works except for the repeat rate function. I'm going to check the power supply pcb and see if I missed another solder ball somewhere.

I feel like an idiot but at least I'm getting somewhere. Haha.
It happens to the best of us. Right now I'm at work and we're trying to figure out how to undo a solder bridge under a 63 contact Ball Grid Array. They aren't really meant to be hand soldered in the first place, much less reworked and at $106 a chip with a two month lead time...

The good thing about your rate problem is that the motor is working. Does your echo cancel footswitch work? Did you check your voltage vs. the DC Brushless Motor Circuit schematic yet? Maybe your problem is around that Q8 because it didn't like whatever happened with the audio probe? It's more likely that something happened with the wires at 51 and 52 going to the repeat rate pot.

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Re: space echo hell

Post by twiitala » Sat Feb 28, 2015 11:39 pm

Yikes, I hope you figured out a way to take care of that chip. That sucks.

So I need to do a better job of cleaning up after myself. I found a tiny solder ball on the power supply board so I removed that and the repeat rate works now.

Now I need to check the bias etc. Do you think it's possible to do the electrical adjustments without an oscilloscope? Or is that the best way?

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Re: space echo hell

Post by Darlington Pair » Wed Mar 11, 2015 10:10 am

twiitala wrote:Yikes, I hope you figured out a way to take care of that chip. That sucks.

So I need to do a better job of cleaning up after myself. I found a tiny solder ball on the power supply board so I removed that and the repeat rate works now.

Now I need to check the bias etc. Do you think it's possible to do the electrical adjustments without an oscilloscope? Or is that the best way?
A scope is nice, but most of the time I use the scope to set it to service manual specs and then tweak by ear from there for my personal preferences. They're pretty forgiving, you can hear the bias changes, intensity, and volume. Once you get a feel of how all of those things sound and how they interact with each other it's pretty easy to do by ear, kinda like biasing a fuzz face, you can use the meter, but at a certain point you just have to play the danged thing and see how it sounds.

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Re: space echo hell

Post by twiitala » Thu Jun 04, 2015 6:40 am

So, my space echo is back together and seems to be working properly...for the most part.

The loop I've made isn't working as well as I'd like since I occasionally hear the splice. When I use the space echo on my voice I don't hear the splice, but I hear it when I play higher notes on the guitar.

Any ideas on what might be causing it? I haven't checked the tape tension yet since I don't have those gauges. I have also not replaced the felts. Would it help to replace those?

Maybe it's my loop?

Does anyone have tips for making a good one? I'm using tape from a Fidelipac cartridge and I have a splicing block and the proper splicing tape. When I hold the loop up to a bright light I see just a little gap in the splice. Is that normal?

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Post by The Scum » Thu Jun 04, 2015 2:01 pm

I've got similar issues...I've tried several kinds of splicing tape, and I still hear it when it goes by.

My interim fix has been to load longer loops, so it doesn't go by as often.

...And to learn to love the warble and dropouts. I mean, I'm using a Space Echo, right? I've got other options if I need pristine.
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Post by twiitala » Thu Jun 04, 2015 5:37 pm

Yeah longer loops help for sure.

There has to be a way to make the sound of the splice go away though. I don't remember hearing it with the original loop when I first got my space echo. I guess I'll have to listen to the tracks I first recorded with it to find out.

Have you swapped out anything on your space echo yet like felts or anything?

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Post by Darlington Pair » Thu Jul 23, 2015 10:34 am

The Scum wrote:I've got similar issues...I've tried several kinds of splicing tape, and I still hear it when it goes by.

My interim fix has been to load longer loops, so it doesn't go by as often.

...And to learn to love the warble and dropouts. I mean, I'm using a Space Echo, right? I've got other options if I need pristine.
Yeah longer loops help for sure.

There has to be a way to make the sound of the splice go away though. I don't remember hearing it with the original loop when I first got my space echo. I guess I'll have to listen to the tracks I first recorded with it to find out.

Have you swapped out anything on your space echo yet like felts or anything?
Yeah, a combo of longer loops, love the splice, and practice.

I grew up in a radio station editing commercials with a razor blade for my dad so I already had a pretty good handle on splicing before I got a space echo. Most of the time my splices are pretty inaudible, but every now and then I get one that's not right. If it's not right in a bad way I pull it away from the heads (I have a splicing block mounted in the older of my two) and resplice it, if it's not right in a good way I spend the next however long it takes to wear out my tape with a fun splice.

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Post by The Scum » Mon Aug 10, 2015 12:39 pm

What cut on the block do you use? Angled?

And what tape do you use? I've had better luck with plain scotch tape than with splicing tape (Ampex, I think it is...). The splicing tape is actually fairly stiff in comparison.
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Post by A.David.MacKinnon » Tue Aug 11, 2015 7:43 pm

The Scum wrote:What cut on the block do you use? Angled?

And what tape do you use? I've had better luck with plain scotch tape than with splicing tape (Ampex, I think it is...). The splicing tape is actually fairly stiff in comparison.
^^^^^This. Same is true for the WEM copicat & 2 space echos at my place (as well as the tape loops I run on the 2 track). Regular splice tape is too stiff and give an audible blip when it passes through the transport. Scotch wears out and comes unstuck faster but leaves no weird audio artifacts.

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