EHX Vintage issues

[txjeff]

So after another hour or so today, I got out the scope. First looking at it as black box, I can vary which of three BBDs I have to test; the OEM one, the one I bought that was untested, and the third one that is claimed to be tested in a breadboard test circuit. We'll call these BBD1, 2 and 3. Second, the Color trim will be fixed at the OEM 10 o'clock position. Batteries are good. Voltages verified. This leaves the BBDs and the VR1 voltage adjust trim as the only variables. To start off, I measured, with the scope, the PP voltage of my guitar signal with FS bypassed and at output with effect on (but no flanging happening with BBD2 in play and VR1 in OEM 1 o'clock position (or 3.5V). As expected, the guitar PP voltage is about half of the fully bypassed height. Which is probably sensible considering it's a blend of dry and wet sign summation that would result in a fatter sound. Also Ralf's description clearly says this version, V2, has less gain in effect mode and later versions added some gain to stage 1 instead of unity gain.

So all that's good. Then I scoped the various clock inputs to BBD and outputs from BBD output pin all the way to components in the output, through to output jack. In effect mode, I can see the wavering waveform achieved by the clock inputs and if I strum the guitar, I can see a combination of waveforms. However, the PP voltage of the final BBD output is a very low level. And it's not audible at full volume of my powered speakers. And this makes me think, if I'm only seeing a resultant waveform at the output of BBD that is from the clock pulses, that's not enough. What I should be seeing is a blend of the guitar signal that is summed with the BBD signal to ultimately make an audible flanged sound. I proceeded to turn the VR1 pot a bit from one direction to the other. I could hear some variations in gain and a little tone but nothing magical, as with BBD1.

And we already know BBD1, with a certain VR1 setting, will achieve some audilbe flanged guitar sound, but distorted.

When I finished checking and testing, I still have to consider, all things being equal in settings and input, and only varying the 3 BBDs, if they all were working similarly, they would all do the same thing. All would start flanging at a similar voltage at the 4558 pin 3, 1.5V. Or, visa versa, would mean all three would behave the same and not flange at all at any of the VR1 settings, such as BBD2 and 3. So it's a given, I can't be confident any of the BBDs I have. All I have is some sort of working flange sound that only gives me some comfort that the rest of the circuitry LFO, VCO, Op Amps, Color feedback and power supply are all doing their job and that the input signal is being processed to the output. Also the filter matrix switch is properly doing it's thing. Although I never found that to be any big whup effect and rarely used it. So I think my decision is to put BBD1 in, return BBD3, throw away BBD2, get it making the pseudo flanging sound and sell it as is, being honest about it's age and limitations. And possibly some expert will buy it who might have other BBDs and can get it back to 100% again. I figure it's really, really close with all the effort I've put into it and the intense point to point tests and component replacements.

[txjeff]

The newer BBD I bought, the seller was nice and refunded my money and said keep the chip anyway. I stumbled upon a guy, Ron Sound who does effect repairs and I'm thinking of Monday calling him and letting him know where I'm at with the effect so far and maybe he will take a look at it and figure out what's going on. (I wish I knew that weeks ago about that place).

[txjeff]

Shipping unit (tomorrow) to Ron Sound in Indiana.

[modman]

Very valuable discussion, but I moved it to the repair section. Did upgrade this thread to sticky.

[txjeff]

Thanks Modman for the move. Still in glass half full thinking that the flanger will be working again, I'm focused now on the replacment metal boxes being fabricated for the flanger, phase shifter and fuzz circuits. That's been several hours of hand drawing, using actual phtotos of other vintage boxes, to get the dimensions and my old drafting skills to sketch out the fabrication drawing for each box. Considering all the work it would take me to drill a bunch of holes and especially the rectangular switch holes, for $50 more, the fabricator is going to do all the holes using a plasma cutter. After knocking out those drawings and meeting up with the fabricator yesterday, the timing was good as he was getting ready to start on them. I got lucky to have a local fabricator 4 miles away from my house. Just frustrated that in the 70s I decided to throw away the original boxes after moving the circuit boards to the one unit never thinking the resale value of individual effects would be as high as it is these days. Grrr.

The other trick is realizing the original boxes use some sort of stencil and painting to do the lettering. Which is why many older boxes look pretty scratched up. An inexpensive way to do it. I found a local laser place that can engrave SS for a very reasonable price. The process etches out the words from a photo in PNG format with transparent background. Then it's a matter of wiping paint of the proper color over the etchings where the color fills in the etching. Of course the decision is to sell these as original guts with new fabricated boxes, and the addition of better more modern power barrel type sockets, for the effect board users.

[txjeff]

Update 2/20: So 7 days since I mailed my flanger to Ron Sound. At first we had good communcation. And the claim was that he would work on it this past weekend, as I sat patiently although on the edge of my seat waiting for a message of the findings. But nothing. So I sent a message Monday asking for an update. Nothing. Then another one early this morning. So far, 2 pm, nothing. Ugh. So frustrating. If I hear nothing by tomorrow, I will call the number and get an update. I simply don't do business that way, and I've had plenty of home type businesses. If I mention a timeframe for completion but there is a problem of some kind, you can bet you will get a call or message from me explaining what's going on and reassuring that I will finish as quickly as humanly possible. Or, if I realize I can't fix something, well that happens too and I might not charge anything for that. Of course, I figured, what else is left but the BBD that is the only real hard to prove focus? If you have a known good one, change it out and you will at least have an immediate one conclusion. If it works, done. If it doesn't work, well that will mean more time.

[txjeff]

Finally got a reply at 6 pm from Ron saying how he's been tied up with work so I have to wait until this weekend. Hmm. Must be a demanding job to not have 20 minutes to swap a BBD chip and see what happens.

[txjeff]

So another weekend passes with no reply from Ron. Totally annoyance. Debating to pull the trigger on just mail it back to me. Just not used to people that behave poorly that often.

[modman]

Well, I think that's quite enough -- Ron is a forum member too, but really has a proper job - quite technical. I'm sure he'll get back to you, but I'm honestly surprised he even took on the job - he probably didn't read this thread...

After all the advice given in this thread and not heeded, there isn't much left than to close it. 50 messages in one thread going nowhere... Hopefully it shows other how to not go about it. Or even: not to even try to fix these old EHX reticon units...