Kasino Bass Natural

[helizond]

Hi all!
I have a Kasino Bass Natural model 150BASS which back in '76 died with a loud whistling sound as I was turning it OFF during a practice session. I took it to a TV repair shop to get it fixed (it was 1976, remember?) The tech guy asked me for a replacement op amp (LM324, I think... quad op amp), which back then were not that easy to get. He got it fixed and it's been working like a charm.

I am getting it back on the road and was checking it out after being in the closet for more than 15 years, and to my dismay I found out that the tech guy replaced some transistors in the amp section, not the op amp as he said!

I would like to restore it to original as much as possible, but have no way of knowing which were the original transistors he replaced, nor any way of knowing if he replaced the power transistors too, not just the ones on the board... though I guess RCA branding on them kind of gives them away, doesn't it?

Does anybody have a diagram for an PC5033 Rev1 board?
And if you have the preamp it would be great too (PC5104 Rev1).

I really appreciate any help I can get.

[Enzo]

It has been posted numerous times here. Either do a search for PC5033 or look near the top of this section for links to Kustom schematics, and scroll down to the PC5033.

And welcome to the forum.

[helizond]

Thank you!

I did an extensive search using Kasino, Natural, and 150bass as keywords, and read all the posts related to diagram requests, but since I did not find anything I just assumed there were none.

I noticed people referring to board numbers, so I opened my amp once again to look up the board numbers, but failed to do a search using them as keywords... my bad.

Again, thanks for your help and for your warm welcome to the forum.

[Enzo]

The Kustom brands were kinda unique, in that they didn't issue schematics for models really. The drawing for a "K100" or whatever would be a block diagram, with blocks for preamp and power amp. Those would be specified as the board number. So starting with a collection of different preamp module boards and some different power amps, they could make up any configuation they wanted and give it a model name. SO when you want the component level circuit diagram, you need the board number.

The PC5033 is one of the most common boards.

[J M Fahey]

Dear helizond, welcome.
I am intrigued by

and to my dismay I found out that the tech guy replaced some transistors in the amp section, not the op amp as he said!

Why "dismay" ?
Do you think he somewhat cheated you, perhaps by using "inferior" components or something like that?
Well, he certainly must have replaced "house number" transistors, by commercially available equivalents, probably the same but with the original label, nothing to worry about.
Transistors are not tubes, are used differently, hundreds of similar spec transistors will sound exactly the same, if used in the same place.
Besides,

He got it fixed and it's been working like a charm.

should be taken in consideration.
Don't worry, just enjoy that fine piece of equipment .... and "don't fix wat's not broken"
Good luck.

[helizond]

I understand about the block diagrams and I think that was a very clever way to do it, thus having modular systems which could be adapted to different configurations according to the specific needs.
So part of the trick in getting an amp fixed is knowing which modules make up your particular amp and then searching the diagram of the specific board that's ailing.
I guess I'm just paying my dues for being the 'newbie' in this forum :-(

I downloaded the diagram for the amp output section, although I'm not sure what kind of heatsink the 40409 and 40410 originally had (the tech guy replaced them with some TO-5 transistors and used some kind of small 'crown-like' heatsink, which makes them stand out from the board and I'm worried because a couple of copper traces are already coming off the board.)

[edit] I just did a GIS for PC5033 and it brought me back to several posts here where I could see what the transistor heatsinks look like... do they really need that much heat dissipation??? What the tech guy used is practically nothing compared to those massive heatsinks. I haven't had any problems with it though, and I actually gigged last night for a couple of hours using it as it is, although it sounded a bit muffled to me... maybe it was just the speaker, so I just switched back to my old (new) setup for the rest of the night.
Anyhow, back to the heat sink. I saw the 40409 transistors going for $15.50, but some people were suggesting using newer versions for reliability, as long as they matched the specs as close as possible. Any ideas on this?

Oh, and I didn't have any luck finding info for the PC5104 board... maybe it isn't that popular at all!

Thanks again for your comments, Enzo.

[helizond]

Well, I was dismayed because he gave me back the 'bad' op amp in a plastic bag along with its data sheet and for years I very carefully kept it just in case I would need it again in the future. So this image of a 14-pin op amp being replaced was fast embedded in my mind, and then finding out that I had held that part so dearly for so many years --I still have it in one of my tool boxes-- just for nothing... it's kind of unsettling, to say the least. And yes, he somehow cheated me, because I had to make a 300-mile trip to get that part... but he got it working again.

I'm not sure he had access to the ECG replacement book back then, he was a good old-fashioned TV tech (had a lot of customers, or maybe he was just located in the right spot), but he got the job done. I'm not even sure of which replacements he used; I didn't see any markings on the transistors when I last opened my amp, and as I said before, the copper traces are coming off, so I don't want to cause any unnecessary stress on them.

Thanks for your comments, and I guess I'll just let it be, since 'it ain't broken'.

Now can anybody tell me, is it normal to expect a 'dull' sound from this amp? That was my impression from last night, although the guitar player liked it (well, he's the guitar player, what can you expect?). I felt the amp was starting to overdrive with the volume knob just halfway, MIM Jazz w/DiMarzio DP149 plugged into channel 2 (ch.1 was too hot), tone controls (bass, bass, and bass... ;-) ) set to 12 o'clock.

I wish I could tell you more, something about voltages, current, oscilloscope traces, frequency response, etc., but right now I don't have access to any test equipment (would love to.... been away from them for so long!) All I have right now is a couple of multimeters, which are good for quiescent measurements but not for the transient response I'm looking for.

Thanks for your good wishes and your wise words of advice, JM.

[J M Fahey]

Thanks.
You do not really need scope traces nor anything else, because it's working perfectly.
Those 40409/40410 were, in practice, TO5 with built-in heatsinks.
The replacements are certainly the equivalent.
The only problem that surfaces now and then, (I've been bitten too) is that PCB designers used the extra heatsink pins , which are there to mechanically fix it, as some kind of jumper.
Often one track gets to one pin, continues from another.
If you do not use the original heatsink, you lose connectivity.
Easily fixed with an inch of wire, of course.
If the transistor is starting to pull the pad, don't wait for it to happen, I think a dab of silicone or hot glue mechanically joining those legs to the board (on the component side) will be good.
On the solder side you might add a "hair" of wire to reinforce the track with a little solder.
As of the amp starting to crunch over half volume, it's normal. Those old amps used no compressors or limiters, which, in my personal opinion, are indispensable on Bass amps.
Tube amps, of course, compress on their own.

[helizond]

Thank you for your clarifications about the sound; crunching being a normal expectation from old amps.

I had read a post where you mentioned about the pads being used as jumpers; in this particular case, they weren't --I just checked the pics I took when trying to identify the board.

Using hot glue to hold the transistors on the component side! Great idea!!

As for the compression/limiting feature you mention, I just got a Peavey Microobass amp from a craigslister. I found out that no matter how hard I tried to drive it during 'unplugged' rehearsal it wouldn't overdrive (not a great deal of volume anyway, but that was expected... well, actually good for its size). Upon checking its diagram I saw there's a very clever feedback circuit that keeps things within safe margin --marvelous thinking! I understand it is a Peavey patent feature and am not sure how well it would work when playing live and having to get more volume out of an amp with that feature.

Oh!
Before I forget!
Yesterday I almost got shocked; I kind of expected it, since my Kasino amp has the original 2-prong power cable and the on-off-on power switch. So I first turned it on to one position and carefully went to the main PA and tapped the frame while barely holding my bass... yep, I had turned it on the wrong way, but it was just a faint shock mitigated by my calloused fingers (not my lips as it has happened before while getting ready to sing!). My question is that if I change the 2-wire to a 3-wire hookup, I must also replace the on-off-on switch for a spst one, breaking the connection to the 'hot' wire, right? Ground goes to chassis and neutral goes to... wherever the neutral is supposed to go (wasn't it the chassis too on those old amps?). I understand this is an exception to the 'ain't broken - don't fix' rule, because it is working, but I might be the one broken if I don't get it fixed!

Thanks again for your comments, JM

[J M Fahey]

You're welcome.
If you wish, you may tap some signal from your MicroBass and use it to drive your Kasino, straight into the power amp (you may add a switching jack between pre and power amp).
A scope will certainly help, but you can set it properly by raising the Master Volume (the one you'll add after the compressor) step by step until it *just* starts crunching, then backup a hair.
Wen I was young, late 60's, early 70's, I used to go see every Buenos Aires band which got a new "imported" amplifier (It meant USA or UK then, and *maybe* the rare Yamaha) and begged /menaced/bribed/whatever until I could get a peek at its innards, to learn something new (still do, he he, old vices die hard).
I remember this guy who had an exotic (for us) Kasino.
A tall handsome beast, a BIG 2x15" cabinet (heavy square magnet Eminences, 2-1/2" aluminum voice coils, aluminum dust caps).
The amp was used on "8" or "10" all the time, the output was a perfect squarewave.
¿Horrible? Believe it or not, quite acceptable.
1) Those 15" speakers were in a too large, underdamped, boomy box, with probably a 6 to 10dB peak at resonance (60/70Hz), plus no useful output above 1500 or 2000 Hz, it filtered the squarewave into a gnarly but interesting sound; quite compressed sounding to boot and buzzy enough to cut through. *Good* oldschool bass cabinet.
2) It was the heyday of Yes, and this guy was *a lot* into Chris Squire, including a Rickenbacker. That Chris *did* use a quite distorted sound didn't hurt either.
3) Of course, If you intend to play good old smokey Blues on that amp, forget it, it will be an excellent Country amp, provided it does not clip.
4) This guy had the 115V version, we use 220V, guess who got "the contract" to rewind the power transformer ? ("Backward Engineering" the full amp as a side operation)
5) Remove completely the grounding capacitor and discard it; the switch may be the same ( more authenticity) but both sides will be "good" now, an improvement.
Your new cable will have live and neutral wires as the one you have now, and the ground wire to a terminal very well secured to chassis. Use a good cable clamp and let the ground wire be one inch longer than the others, so in the unlikely but not impossible case that somebody yanks the cable, the last one to break will be the ground one.
6) Play some Creedence licks through it, for authenticity.

[helizond]

I got the Creedence part already!

I'm going to get a good piece of 3-wire cable, although I'm not sure if it will be as long as the original one... I don't remember EVER using that much cable during setup for a gig. I'll get rid of the grounding cap, I think I need to rewire the switch to be on-off-on with no polarity reversal, and make sure I get a good crimping connector for the ground wire and connect it to the chassis.

I had a valve amp with a curious brand name, TENNA. I'm not sure what happened to it... I left it at a friend's house and the rest is history (that was back in '82). This amp was hooked up to a 2x15" cab, and after a couple of minutes would go into some kind of 'overdrive' mode, which I think is similar to the Kasino with the 2x15 you mention. I was never really into tubes, so I did not dare getting into it and try solving the problem; I had the Kasino and somehow traded the 2 15" for a Dynaco amp that I needed back then (and I still have it working!) Anyhow, the TENNA output was a bit unpredictable for what we were doing, so maybe that's why it got left behind.

As to using the Microbass as a preamp... I thought the 4558s they use for preamp would be a bit 'noisy', aren't they? And about going into the power amp... oh, wait a minute... you mean the Kasino power amp when talking about pre and power amp! Well about a bit more than 25 years ago I added a buffer circuit between the Kasino's pre and the amp in order to be able to have a compressor (a PAIA kit, I reckon). I just took it out for sake of having the least amount of possible trouble spots for last Friday's gig, and besides, I don't remember what kind of design I did; I used a TL082 opamp and had a pot to control the gain of the effect loop... not sure if I will put it in again. I don't see any need to right now, at least.

You threw me off with the "straight into the power amp" part, but then I saw the "Master Volume (the one you'll add..." part, and realized I was now headed in the right direction. So if I understand correctly, you're suggesting taking the output from the Microbass (headphone, I assume) and feeding it through a master volume control to the Kasino main amp... wouldn't this require a high value pot (power-wise, I mean)? I would love to be able to take the signal out of the Microbass before its main amp, but that's where the feedback circuit takes its signal for control.

Well, I guess that leaves some room for thought and experimentation.

Thank you again for your insights and comments.

Oh! You never said what amp it was that you back-engin... I mean, fixed the power transformer! :-)

[J M Fahey]

1) Congratulations.
2) Now that you mention it, I had almost forgotten, they *did* use long power cables way back then !!
3) No need to rewire the power switch, inverting phase is the same to that transformer, what's important is to secure properly that ground wire, and of course, no grounding cap.
4) Those 4558 are good.
5) Since the Peavey compressor involves its power amp, pulling signal from its preamp won't do , and headphone signal is too high. You should copy what old Randalls, Peaveys, Kustoms did, their "booster" or "line" out: the signal which goes to the speaker, which usually is around 20V RMS, padded down vy two resistors, typically a 10K from "hot" and a 470 ohm or 1K to ground.
You are padding down the signal to about a very reasonable 1 volt.
Wire a Line Out level 10K pot across that 470/1K resistor to control how much you send to the Kasino.
Send that to a new jack in the Peavey back panel and label it line out.
You will still hear music through its speaker.
6) In your Kasino backpanel put a "switching jack" between the preamp and power amp.
With nothing plugged, the Kasino signal goes straight through; if you plug the Peavey signal, that's what you'll hear.
If in doubt, study the "Loop/power in" used by other amps.
You set the send level pot just once: play the Peavey until it clearly compresses, then rise the new Master level (from "0") until the kasino (deafening volume) just starts to crunch.
Leave it there and forget it. Play and get murderous looks from the others, you will be *loud*.
For bedroom playing just use the Peavey, nothing has changed for it.
7) I still must have somewhare a yellowing spiral bound notebook with assorted hand traced schematic snips.
Not the full one , but what I thought was special or unique in that particular amp.
The idea was not cloning but learning.
In that particular case, the amp and preamp were basically conventional, the special part was the Bright control which *always* worked and was quite strong, compared to, say, a Fender Bright which was lighter (you would notice it on a guitar, very little on Bass) and would not work with the volume on "10".
The real special part was that big beefy loud 2x15" box.

[helizond]

Let me see if I got you right.
What I understand you're suggesting is something like this:


(gave up trying to set it in ASCII here!)

It took me a while trying to understand the reasoning behind getting the Peavey to work as a compressor since the Kasino would crunch the signal anyway, but reading over your description again it makes sense after all (given that I take the necessary measures to match the signals correctly... that's the key).
And if I understand correctly, the 10K pot would be just a preset.

Thanks for your help!

[J M Fahey]

Yes, that's basically it.
Thanks to its built-in compressor, the Peavey will *never* clip, which means that it's peak output levelis set to a *fixed* point, ehich it will never surpass.
Your Kasino has fixed gain; if you set that limited signal input to *just* the Kasino clipping level, it will not go beyond that.
In theory you should use a scope to set it, but playing the Peavey until it clearly limits (easy to hear) and rising the Kasino level until it *just * clips is the same.
For very clean Hi Fi work, back up a little; for MI sound, let it crunch *a little*, it will give it more presence onstage.

[helizond]

"Crunch a little" and "more presence onstage"...
I like that!!!