standell "reverbalux" adineko oil can delay unit advice sought

[pinkjimiphoton]

hey guys,





well, almost a year later, i finally got back to this last nite. i got it working, and found a couple mistakes on the schematic where stuff was off by a factor of 10 or 100x... the mixer resistor before the output, shown as 47k needs to be more like 4.7k. probing around with an audio probe last nite i found i had  plenty of wet on the tube side and plenty of dry on the pot side. so it HAD to be the 47k. replaced it with a 10k 1/2 watt resistor, and it improved immensely.  tacked another in parallel for about a 5k load <all my resistors are 1/8th and 1/4 watt> and suddenly i had a decent mix of echo and dry. so i'm assuming the original schematic may have a mistake on it, its easy to confuse color bands after years and years.

also, the 2 cathode bypass caps seem to want 22uf, not .22uf. so i changed them out. cleaner better stronger signal, the distortion on the echoes is mostly gone.

changed the 2 valves to 12ax7. that helped a bit, too.

discovered upon tracing thru the cct, it HAD been modified at some point. someone added a 10n cap to ground just after the 10m/10n input cap node. also had both cathode bypass caps connected to the wrong holes in the circuit board, and a 100k to ABSOLUTELY NOTHING tied to the 4.7 n off the pate of the second stage. a mystery resistor.

also, as shown on the schematic, at least on mine, the schematic splits the tubes differently from whats shown... the two top triodes are one half of each tube, the bottom two are the other halves, but reversed from what's shown. confusing!

removing the bad connections and removing the extra parts and reconnecting stuff right went far and quickly.

so now, it lives again, tho i need to hit the jobber and get a couple proper parts for it.

btw, for cathode bypass caps and the mixer stage, 25-50v caps is plenty... only dealing with a couple volts there. the n/p cap is only seeing about 5 volts max on either side <less than that, even>

the 22uFnp cap i used @50v is fine. 10-22uF shouldn't make much diff.

i topped off some more goo into it, i found if it was laying on its side while i was working on it with the goo immersing the  disc it worked better, so i added a bit more to it. its hard to tell if it really helped or not.

so.... i gotta couple questions now...


is it ok to recycle the goo if i pour it out to clean the can and brushes?


is there a way to clean the head/brushes/rubber things to get a bit more oomph out of the cct?


i tried temporarily replacing the cathode resistor to ground from the echo return stage where it has the 2.2k/100k node with a 10k instead of the 100 to see if i could get more echo balls. it didn't help. looking at it, maybe i should try a 1m there instead? its been literally decades since i really messed with anything with toobs in it.
or would i do better to decrease the 2.2m resistor?

any ideas on how to get a little more wet signal? its pretty close to matched, volume wise, but i'd like a hair more wet. its not as ballsy as my old telray was <i used to have one of the ones with the built in "fuzz">

i appreciate the advice. i look forward to finishing this thing finally!

[anotherjim]

The playback doesn't seem to have any gain, the one tube is just a buffer and the mixing after all passive and lossy -  so I only see scope to boost the recording level. That 100k feeding "B" is actually a plate load, and can be bigger which might give a bit more gain. Try 220k.

Mad jealous you have one of those to play with 

Tank oil is probably some kind of extra pure mineral oil. Best quality like for sewing machines and food safe.

[pinkjimiphoton]

the tank oil... which i dumped all over my bench last nite.. is some kinda weird shit union carbide made in the 60's. i have a bottle of it, ub 65.

i've played with the circuit quite a bit. the only things that have helped were ditching the 47k to ground off the np cap.. that brought the slap up to unity... and making the 47k mixing resistor 4.7k instead.

increasing the gain just makes it distort more. reducing that one plate load resistor to 68k helped increase the volume.. everythings being run at about 50 volts or so, so the tubes are fairly starved. the reverb return/feedback amp i may have a play with to try and increase its headroom. its already got a 270k anode resistor, i am gonna try to take it up to 470k, and if that just makes it overdrive more, will drop it down to around 100k and see if the increase in voltage helps a little. its all a balancing act thru that cheezy ass capacitive mixer.

also thinking bigger coupling caps may help, but there's only so much you can do with these kind of systems.

interestingly, the footswitch jack is just wet signal and sounds great. but none of the knobs work other than the "echo select" one. the echo volume becomes a tone control, and the reverb control has little to no effect.

i raised the cathode caps from .22uF to 22uF and that helped quite a bit.. stronger signal, less ripple. it sounds VERY clean now, but i need to get that wet signal hotter.

bypassing the 47k mix resistor gets the echo hot enough, but then its kinda distorted. 4.7k seems to be what they probably meant to have in there.

i may try and hack in one of jack's mosfet boosters into it to see if i can get it wetter. its doing the slap thing, but out of the output jack mixer, i'm only getting maybe 2 slaps max, where as its a lot wetter out of the footswitch jack. so i gotta definitely get that signal stronger, i think.

also went to 12ax7's for both bottles. now its a touch above unity gain, where before it was just under.

the thing sounds great. maybe we should make a stomp preamp out of it

we could call it an ep boost or some...err...

i'll keep dicking with it.  thanks for the input, jimmy!

[pinkjimiphoton]

got it!
when all was said and done, mostly it came down to a couple circuit changes and bad coupling caps.

the 47k to ground resistor is now 1 meg. that brought up the echo considerably.

the 47k resistor i'd changed out to 4.7k in the mixer section was changed to a 68n cap. now there's some echo getting thru from the tank, and the reverb and mix pots actually DO something.

made the cap to the wiper of the echo pot 22n instead of 10n

made the 1n cap to the grid of the second stage  82n. brought the echo completely back to life.

had to add a 220p snubber to ground from the pot side of the 10n cap to the echo pot <now 22n>. took out the ground hum it had. 470p was better, but took too much of the echo away.

made the np "mixer cap" 22uf np instead of 10. works great, pretty much most values will work in this circuit. its all just a matter of finding the changes that will be toneful.

i DID try different values in almost every location trying to fine tune it. i'll up a schematic revision when i get a chance to draw in the value changes.

its not the totally vintage circuit, but its been brought up a bit closer to modern standards. it went from wimpy worthless and weak to nice and robust, like i remember my original telray sounding, but this is much much cleaner. used all 630v caps, but its overkill... most of the circuit runs on just 50 volts.

anyways.. more later, maybe even a quick demo sometime soon.

[pinkjimiphoton]

here's a schematic with the mods i made. notice there's really only a couple changes, and a couple value changes. but now the echo works, the reverb works, its strong and wet and actually sounds pretty good!

[SatchmoeddieII]

Union Carbide still makes that oil, but you have to buy a 55 gallon drum of the stuff for around $2400 including taxes & lift gate truck shipping. You can blend different PAG oils to get the correct viscosity. Those come in smaller quantities like 1 quart bottles.

[pinkjimiphoton]

gotta couple bottles of it on ebay years ago. will last forever...at least from my limited perspective lol

[CheapPedalCollector]

The power supply design is terrible like in most Tel-Ray devices. I bet it hums quite a bit, not sure I like the HT secondary grounded to chassis either, I would put an HT fuse in there for safety. Does it have a C.T. ? Full wave would be less noisy too.

I bet that neon bulb makes racket too.

[pinkjimiphoton]

haven't looked inside it in years bro... no idea. doesn't hum. but the mixer stage between dry and wet is @#$%ed up as a soup sandwich, basically uses an np cap to mix the dry and wet signal.