Peavey Classic 30

speak of the devil,

yes this amp is  a pain to work on, kind of like Peavey meets Behringer, not like most PV's which are usually a joy to work on,

takes a lot of work to get the chassis out, plastic tube cover, 8 chassis bolts, two strain reliefs, and one reverb pan,

but the PC board will be  cake walk, right?

wrong.

funky U shaped channel that requires folding the thing together like you were compressing a Subway foot long salami and swiss grinder,  hope and pray you do not break a pot of start snapping PC board jumpers.

a previous thread on this amp called attention to the fact that there might be a funky screen resistor thing going on,

and we had one bad EL84 tube out of four, which suggests red plating on one side of the push pull circuit,

so we up the 100 ohms to 470 - 3 Watt and think about adding screen resistors to the other two tubes,

here is the PC sandwich with extra onions, main problem with amp besides one weak tube was that the 400 ohm pwr supply resistor opened up, they have it up on stilts where it can catch standing waves as this amp is known to have a very resonant cabinet, we notice that pwr resistors do not like vibration, their own weight is their worst enemy, providing inertial mass that resists accelerations along the space-time continuem.  this usually results in an open lead,

we use a 350 ohm 10 watt and jb weld it to the chassis for less vibration and bullet proof heat sinking. use tie wraps also in case the jb weld gets too hot,

since this amp uses pc mount tube sockets, we had no way to implement two more screen resistors, searching for pc board jumpers where they could be inserted was a no go, however, we did notice that after the screens are tied together, there was a pc board jumper that was just waiting for a 220 ohm (since we have two tubes in parallel) 5 watt resistor,

you can not mount it on the top of the board as it will bottom out when you go to install the chassis so we put it underneath,

so now we have an amp that will not eat tubes (hopefully) or lose the pwr supply.

what else can we do before we put the sandwich back in the refer?

heard some rumble about tone caps a while back,

here is a link>

http://blueguitar.org/new/articles/b...30_origmod.pdf

here is a stock PV ceramic tone cap next to what we stuck in there,

now we are ready to play for pay, and maybe get a cheeseburger from the bar maid,

**** I hate the design of these...I have a power tranny for one if you need it. Peavey filament scheme tho.

Thanks CJ for sharing. I'll be checking the Classic 50 here for resitor-additions. The 50 is not identical, but alike PCB-folding approach... 

clintrubber said:

but alike PCB-folding approach... 

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I may have been the first engineer at Peavey to use that wire jumper board folding packaging approach. The wire jumpers were cheap, machine inserted and could use different lengths (just a long roll of solid wire on the machine that gets cut to length). Before the separate PCBs get broken out of the panel they lay flat so can be wave soldered like one large PCB (less individual handling in the factory means less labor cost, and the right number of subassemblies are always together).

I did an inexpensive line mixer using vertical pots and switches on the front panel with vertical jacks for the rear panel, with zero point to point wiring inside or any additional assembly labor other than to fold up the PCB and pop it into the metal.  My boss made cost engineering re-check their numbers because the labor cost was so low they didn't believe it at first..  8)

The wire jumpers do not like being unbent and re-bent too many times but are robust if bent once for final assembly and left in place. During repairs do not stress the wire jumpers too much because like any solid wire they will break if bent back and forth repeatedly. 

JR

JohnRoberts said:

The wire jumpers do not like being unbent and re-bent too many times but are robust if bent once for final assembly and left in place. During repairs do not stress the wire jumpers too much because like any solid wire they will break if bent back and forth repeatedly. 

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Thanks for the background (& the confession  : it sounds like a valid thing to do for an amp at this pricepoint, let's be realistic  ).

The Classic 50 here still doing OK, but I well realize that modding & upgrading and whatnot might well go at the expense of the reliability of the amp.

Have a Rivera-era Fender solid state amp here which does have such a problem. Uses connectors in addition. So I guess best to tackle it once & for all by replacing those ribbon cables & connectors by 'multiwire/litze' type ribbon-cables & skip the connectors at the same time. 

Ah, so it was your bright idea JR! So tell me, what was your cunning plan for servicing in the field?

it brought the retail price down so low that you just buy a new one,

radardoug said:

Ah, so it was your bright idea JR! So tell me, what was your cunning plan for servicing in the field?

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Do you really want to go there? For a while I was in charge of all the different product managers at Peavey and one thing they (we) learned was that customers do not give a flying fsck about serviceability at POS (dealers care, customers not so much). Likewise they don't care where it was made either (again dealers cared more than customers). They mainly care about what it cost them on that day, and how the price compares to the other brand on the shelf next to it.  The unfortunate reality even back then was that dealers had less and less influence over customer purchase decisions, today is probably even worse.

I had some long soul searching discussions with my speaker product manager about how do you communicate to customers about the feature of repairable speaker drivers? Unsophisticated customers do not want to hear about their new speakers blowing up when making purchase decisions (unless they are more professional and can appreciate total lifetime cost).

The Peavey power amps, especially CS series were famous for repairability and significant cost was engineered, hidden inside, where the POS customer could not see it, or appreciate it. But back then $1/watt was inexpensive for an amp, no longer the case.

As I like to repeat, the customer drives all these decisions, since repairability is just another "feature" that customers can decide to pay up for or not. They stopped supporting this with their purchase dollars (at least in value products).

The customer is always right, even when horribly wrong.  8)   

JR

The customer is always right, even when horribly wrong.  8)   

So true!

JohnRoberts said:

.... about how do you communicate to customers about the feature of repairable speaker drivers?

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That was a really cool concept. Recone a speaker with just a 3/16 allen wrench in two minutes. I have done many. And change sizes if you want while you are at it, the Black Widow magnet structures were all the same for any of them .For anyone not familiar with Peavey recone kits, it included the aluminum basket, already glued and lined up as one piece. You were just three 1/4-20 allen bolts away from done (after cleaning the gap), and they always lined right up, no rubbing. Simply bolt the new basket on to your magnet structure.

The Peavey power amps, especially CS series were famous for repairability ...

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You ain't kidding there. Those CS-800s were a wet dream to work on.  Four phillips screws and three 1/4" hex heads got the top cover off, and six more hex heads got both channel heatsinks out, with enough wire length to go to "spread eagle mode" on the bench, without disconnecting anything at all. Everything was accessible to troubleshoot, although it was almost always those damn Motorola TO-3 outputs, one of them would  be shorted E-C. Replace one output transistor, and, of course, that "anti speaker smoke" triac crowbar at the output that responds to DC. The later RCA's that Peavey used, are much more dependable in these 40 year old amps. Next time I repair a Peavey with a bad Motorola output, I will remove the top and inspect for tin whiskers. Just a theory.

Gene

bells and whistles, that's the problem,

for the price of a classic 30 you could build a peg board Champ amp, complete ease of service, 5 minutes in and out,

but people want dual channel with switchable overdrive on each, effects loops, this, that and the other, this saves buying a stomp box to overdrive the front end, so now you are stealing money from Boss and DOD,

makes for a complex circuit board, look inside an Egnater 4 channel or Mesa Boogie if you want to see your worst service nightmare,

the classic 30 was not that bad once you knew how to do it, but you may not want to do that more than 5 times or else, not a tweakers amp, that's for  sure

money might be tight at PV right now, their service dept seems understaffed and took a long vacation for the holidays, and the parts lady was complaining about the atiquated computer system,

I've pondered an after-market remake PCB set for the Classic 30.  You could do a few tweaks like the tone stack and coupling caps, screen resistors, but you also have things you can't really fix like that heater arrangement.  A different power transformer would enable some options, but that's alot more expensive than just swapping out the PCB.

TheJames said:

I've pondered an after-market remake PCB set for the Classic 30.  You could do a few tweaks like the tone stack and coupling caps, screen resistors,

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Interesting thought. For bigger PCB numbers, who knows a-one-design-fits-all could cater for the full Classic tweed range (so the 50 as well, and while at it, that tremolo-circuit could perhaps crammed in as well, with two additional knobs - OK, that's becoming too greedy, you'd need an additional FS-wire as well to switch it on/off, that all gets too busy....)

but you also have things you can't really fix like that heater arrangement.  A different power transformer would enable some options, but that's alot more expensive than just swapping out the PCB.

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Perhaps adding a separate small TX for the heater - not elegant, but can be cheaper.
OK... but while the heater arrangement is sure a bit weird, and sure a hassle when swapping tubes, in the end you'd have all sockets loaded, could live with it.

Regards

TheJames said:

I've pondered an after-market remake PCB set for the Classic 30. 

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And whatever you come up with will cost significantly more than the amp itself and certainly many of its competitors. And at that point, why wouldn't the customer just buy something else?

Or make it a wolf in tweed clothes... 

FWIW... PCB-less, tagboard, or whichever alternative method that suits tweaking.

Can't imagine there aren't any Peavey '~tweed' Classics around that have a second life as a donor for the cabinet & chassis. 

This would be an educational exercise about product design... I used to share a common lab space with the guitar amp engineers at Peavey and I don't recall the layouts being trivial or inconsequential.  While i do not have specific recollections about that amp series, I do recall discussions with knowledgeable designers about subtle things that contributed to a given amp's signature sound.

When you throw a bunch of high gain, high impedance, circuits together in a modest space there will be interactions (like crosstalk) for better and worse. Most of the old Peavey designs were single sided PCBs.  I don't know if you can even buy single sided PCB from most modern vendors (they'll just etch off the unwanted side).

One would be very tempted to use the second PCB layer for shielding since you are paying for it, but in the process likely alter the "sound" of the amp.  Do not expect the first pass to magically be the keeper, so maybe count on several iterations, like the original designers did... Amps with near identical schematics can sound different based on layout.

Good luck and have fun... if anything you will learn something.

JR

PS: maybe drop by NAMM show booth 5299 and ask James Brown about amp design, but he may be busy selling pedals. 

James Brown is a great guy and his amp knowledge is extensive.  No doubt PCB design is a difficult task with all sorts of interesting gotchas.

If you're going to design something like this, you almost have to take into consideration the same manufacturing concerns as the original design.  Only the really hard-core DIY'ers are going to be drilling holes and hand wiring a bunch of pots/switches.  Again...Looking at a larger user base and not just hard-core DIY guys (afterall, you need numbers to make this project worthwhile), you need this to be plug and play with the existing chassis (no new holes), and use the existing chassis/iron.  So you make a board design with the same mounting standoffs and tube socket locations to start with.  You should probably use the same connectors for the transformers.

Since the tubes are on one side of the chassis, and the controls are on the other, you either need to hand-wire the pots/switches, or you build a second board for them.  My vote was for a board.  This presents some issues.  The good is that you can use the pots to hold the whole assembly to the chassis.  The bad is you need to have some method of getting signals back and forth to the main PCB.  You also have the issue with the switches.  You're starting to look at some custom switches or plastic now.  I already committed myself to not having the input jack on the PCB and instead wiring it directly to the main PCB.

It's not a bad project idea, and one I wouldn't be opposed to participating in, but it's a little difficult without the resources of a larger company to source some of the custom stuff you need (like say pots/switches).  Assuming you can find all off-the-shelf parts for everything, the actual cost of the swap kit would be in the neighborhood of about $150 or so.  (PCB's $50, sockets $20, small parts $30, pots/switches/jacks, $30, and some incidental parts).

So for the paint by numbers folks:  Buy PCB set, buy small parts, solder everything together, remove old PCB,  mount new boards. wire up input jack, attach transformers, button up amp.