[Revisit EP250 output issue] See Apr 20 posts on

Jerry Overstreet · From: Louisville Ky

Hi all. I have this old Electra EP250 delay and reverb unit. The delay is analog and the reverb is a long pan spring unit. It sounds great.

The issue is that it attenuates the amp volume more than I would like. I would expect there would be unity gain in one position or other but no.

The output switch positions 40, 20 and 0 db., but it seems to only affect the actual amount of wet/dry and has no effect on the level.

I run the instrument level knob wide open connected through the -30db input jack, which is the stronger of the two inst. inputs, and out the mix jack to the amp input. It's a tad better using the mic channel but not much.

Does this seem normal? Doesn't seem so to me.

Donny Hinson · From: Glen Burnie, Md. U.S.A.

It's a very old unit, probably made 40+ years ago. That the -30db input is stronger than the -20db input is indicative of a problem...the -20db should be noticeable louder.

I'd get it serviced if you want to use it, as the electrolytics are probably nearing the end of their life expectancy.

Jerry Overstreet · From: Louisville Ky

Jack Hanson · From: San Luis Valley, USA

Cool old Silvertone!

Georg Sørtun · From: Mandal, Agder, Norway

Jerry Overstreet · From: Louisville Ky

Thanks Georg. Yes, that's the way the inputs behave. My concern is that at it's loudest output, it is still attenuated and quite a bit less than the amp alone.

Maybe it's just the nature of the beast.

Using a larger amp, such as my NV400, it is more manageable. It is particularly noticeable with the old Silvertone but still usable either way.

Thanks Jack. Yes, that's a 1482 that's been through Ken Fox's shop. I received it through my Uncle's estate. I still have the beat up old box form when he purchased it. 1968, Sears and Roebuck in Louisville as I recall.

It's a treasured old amp for several reasons.

Fred Treece · From: California, USA

The output switch should be loudest at 0dB.
This YouTube fellow is a bit perplexed by the ratings labels too. Georg has covered the input conundrum, but the output should make more sense.
He discusses the input at about 2:50 and the output at around 3:50.
https://m.youtube.com/watch?v=iRQa38Mj2Ks

Jerry Overstreet · From: Louisville Ky

Thanks Fred. I had not seen that YT video. That confirms the inputs operation.

I'll have to revisit that output pad operation, but the perception has been more effect instead of more volume....which was my concern.

I've had it for a year or more but I'll spend some more time with it. We'll see.

Jerry Overstreet · From: Louisville Ky

Well, a lot has happened since I posted this. I haven't really had time to mess with this unit until lately.

The issue I posted about was a lack of output volume. The input from Georg and Fred and the online videos I find is correct on how it's supposed to work.

So, to update and further explain...this is how it behaves:

The signal is strong through the DELAY OUT and the output pad switch operates like it should on the 3 settings for output levels.

The switch does nothing through the MIX OUT jack however, and the volume is attenuated to the lowest level. It appears that the switch is operating correctly, but there's something wrong in the MIX OUT circuitry.

I'm going to open it up again and was wondering if anyone has any idea what to look for. It's all printed circuits and I will recognize anything obvious, but that's it.

This is a great unit and I'd like to get it operating like it should. There's almost nothing online.

Thanks for your help.

Fred Treece · From: California, USA

The mix out jack is probably the one that got used the most. Maybe youâ€™ll get lucky and itâ€™s just worn out, or the contacts are loose, or the tip arm is bent or cruddy. If it's something on the board, youâ€™ll need more than good luck, which is about all I can offer you ðŸ¤”

Jerry Overstreet · From: Louisville Ky

I dunno Fred. It passes sound through the jack, but it might still be bad. I'll open it up in a day or two and look for any obvious faults.

When it was delivered, the rev. tank adhesive had failed and it was rattling in the case....could have damaged something, I suppose.

Jerry Overstreet · From: Louisville Ky

Here's a shot of the innards. The red wire goes to the MIX jack and the Green to DELAY. There are 3 tiny black wires on ea. side of the switch that run to the little circuit board there.

Hopefully someone out there has some ideas.

The Blue arrow is the output dB switch.

The Yellow is the circuit board that is connected to it.

Fred Treece · From: California, USA

It looks like something got clipped off the mix jack terminal next to the one with the red lead connected. Just an observation, you may have already taken note and/or dismissed it.

Carl Gallagher · From: New York, USA

Before I start chasing my tail with a unit this old, I'd change all the electro's.On tube amps I change the power filters every 10 yrs or so.On these lower powered solid state units you will get a longer usable life,but if the unit sat unused for a number of years those caps are surely about done.When an electro doesnt pass current for long periods the electrolite dries out, cap doesnt work efficiently.If the power supply isnt up to par many bad things can happen.

Jerry Overstreet · From: Louisville Ky

ajm · From: Los Angeles

There are a couple of other possibilities.

Design: Maybe that is inherent to the design of the unit (the volume being low).
If that is the case, unless you mod the unit then there isn't much else to do.

Impedance mismatch: Maybe there is an impedance mismatch between the unit and the amp you're using.
Using a worst case scenario, if the output impedance of the unit is really high, and/or the input impedance of the amp is really low, that could cause problems.
By the way, I don't recall if you said what the chain is in your signal path. Something else could be monkeying around causing problems as well.

I have a couple of "newer" effects that lower the volume and/or muffle the highs.
One of them is a buffered bypass pedal, and it does it even when the effect is witched out.
Unless the signal path and impedances are ideal, they will cause problems.

Jerry Overstreet · From: Louisville Ky

If I may repeat:

Jerry Overstreet · From: Louisville Ky

OK, well I give up. I found no broken traces or opens in the wiring. I have determined the output switch works but only affects the amount of the wet signal through the MIX out jack.

The volume is about half what if should be, so I guess I'll need someone qualified to investigate it.

If one of our forum brothers is experienced with this type unit, I would probably be willing to send it to them. I'm not going to send it off to some unknown electronics hut where the service fee might be more than the thing is worth.

I've wanted one of these for a long time and I'd really like to get it working like it's supposed to, but I'm not going to drop big bucks on it.

There were several names on these besides Electra so I'm not sure who the mfg. was.

I think Evans, Multivox, Ibanez, Yamaha et al. From the late 70s thru part of the 80s. Thx all.

George Biner · From: Los Angeles, CA

You've got 6 resistors: representing the 3 attenuation choices for each one of MIX and DELAY. I can see in the photo of the board that there are 3 different resistor values, and there are 2 of each. That all seems OK.

Since the DELAY is unaffected by the dB switch, there must be something up with the switch or the resistor board. But, the switch should do *something* to the MIX signal, but you say it's not doing anything -- that's odd and the only thing that doesn't make sense.

It's hard to see, but in the picture of the top of the resistor board, it looks like you may have a cold solder joint on the upper left black wire. Check to make sure that the solder is not dimpled where the wire comes in. Ideally, you should check continuity there.

It should be easy to troubleshoot with a VOM because each MIX and DELAY are wired the same so you can compare one to the other.

If the electrolytic caps were bad, I think you would hear a lot of buzzing, so I don't think that's a factor.

I can help you further if you take some more detailed pictures of the wiring of the switch, and how the switch is constructed.
_________________
Guacamole Mafia - acoustic harmony duo
Electrical engineer / amp tech in West Los Angeles -- I fix Peaveys
"Now there is a snappy sounding instrument. That f****r really sings." - Jerry Garcia

Jerry Overstreet · From: Louisville Ky

Ha! I just put the thing back together. Laughing

I'm not opposed to disassembly though.

First let me clarify. The dB switch DOES work normally out of the DELAY jack. The 3 positions affect the output volume as they should.

In the MIX jack, the dB switch only appears to affect the amount of the wet signal. It has no effect on the volume. I run the unit vol. control wide open and have to really crank the amp volume to have any usable volume. It's only half or less volume of the DELAY output.

I'll have to wait a few days, but I can open it back up and maybe take some better pics and reflow the solder on the connection you reference. I have confirmed continuity on all the connections in those circuits shown.

The switch is enclosed so I can't really see anything inside. It has 4 identical connections on either side of it which correspond to the respective jack. The connections are visible on the back of it in the photo above the last one posted.

I appreciate your input and offer to help George.

George Biner · From: Los Angeles, CA

OK, please don't rush on my account.

It doesn't make sense that the dB switch would only vary the amount of wet in the MIX output -- it doesn't have the capability to do that, it can only raise or lower the signal it gets, whether it's wet or dry. (You did say earlier that the switch had no effect on the MIX, so need to verify that. ) If the dB switch is switching levels, then it's working and you likely have a larger problem because it's somewhere else in the box with no schematics.

Also, from the pic of the switch it looks like it has 6 contacts, but I suspect that it should have 8 -- there are 6 black wires, one red, and one green. I thought there might be more contacts that I couldn't see. Need clarification on that -- where do all the black wires go?

I hate having no schematic, makes it tougher.
_________________
Guacamole Mafia - acoustic harmony duo
Electrical engineer / amp tech in West Los Angeles -- I fix Peaveys
"Now there is a snappy sounding instrument. That f****r really sings." - Jerry Garcia

Jerry Overstreet · From: Louisville Ky

George Biner · From: Los Angeles, CA

The dB switch and resistor board cannot affect the level of wet/dry -- that is determined upstream.

One thing you can do is desolder the shielded signal wire coming into the resistor board and connect it directly to the output (or a temporary output jack), thus bypassing the attenuator section -- that will tell you if that section is bad. You can then leave it there permanently if you don't need the attenuator function.

Also, you can just take the signal output you have, put it through a small mixer, and gain it up so it's enough for your amps -- more equipment but solves the problem. The price to pay for running cool vintage gear!

Apparently these were made by St. Louis Music. Normally I'd say I'd take a look at it but with no schematic I won't propose that. Hopefully you can find someone local with troubleshooting/soldering skills.

I'd still love to look at more pictures if you have them.
_________________
Guacamole Mafia - acoustic harmony duo
Electrical engineer / amp tech in West Los Angeles -- I fix Peaveys
"Now there is a snappy sounding instrument. That f****r really sings." - Jerry Garcia

Jerry Overstreet · From: Louisville Ky

George, you are the man! Thanks for your follow up. I was ready to give up on it, but after your last post I decided to take another look.

I bypassed the switch and board, wired the MIX jack straight to the lead that goes to the MIX side of the unit. Voila! There is a ton of volume now and nothing else appears to be affected.

I have tons of gain and power now. No PEAK indicator constantly lit and no unintended distortion.

I've gotta go back and make the connections permanent and button 'er up and I'll be ready.

Thank you so much for your help. I owe you one.

While we're here, someone asked about the reverb pan so here's a photo. It's 2 springs about 13 1/2 in. long.

I know back in the 70s and 80s several guitar and steel players used these for awhile and I always wanted one, but never could make it happen. Now that the output is where it needs to be, I'm thrilled old school style.

George Biner · From: Los Angeles, CA

I am so glad that worked! I love old gear and hate to see it dead or sick!

I'm not fully understanding how the peak light was coming on and the distortion, etc, but now we know the attenuation switch or board has a problem -- and it wouldn't be hard to analyze as it's a pretty simple circuit. The resistor board can be repaired, but finding a replacement switch would I think be pretty difficult.
_________________
Guacamole Mafia - acoustic harmony duo
Electrical engineer / amp tech in West Los Angeles -- I fix Peaveys
"Now there is a snappy sounding instrument. That f****r really sings." - Jerry Garcia

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