Friedman Runt 50: "Customer states..."

Peegoo

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I owned a Friedman Pink Taco about 10 years back, so I'm a fan of this brand. They are known for quality of construction and great sound.

This is a long story...

A pal of mine called me up two weeks ago to ask me if I could help him fix his Friedman. It's two months old (still brand new) and for the past three weeks has been acting up. I asked what the issues are and he described the tone controls of the overdrive channel being really weird. The treble control was acting like a volume control and the mid and bass controls did nothing. I suggested he contact Dave Friedman and describe the issue.

A week later he came back and said Dave suggested it may be one or more pots being bad (they apparently have had some reliability issues with the pot assemblies...more on that later) and he would send my pal replacements. I asked if me working on it would void the warranty, and he said he asked the question; Friedman stated the pots are "plug-in" replacements. All that's necessary is to remove the knob, remove the plug from the board, Remove the mounting nut, and reinstall the new pot. Fine--I'll do it.

The parts came in so this morning my pal brought the amp over and I warmed it up to see what the issue was. Yup: the tone control on the dirt channel was acting like a volume/gain control. On the low side it was quiet and clean. Dialed up it got loud and dirty. The master vol was working fine, and the mid and bass controls were not working at all throughout their range.

I drained the caps, pulled the plugs for the three pots and tested them, and they all tested just fine, all the way to their plug pins. Strange. I tested the replacement pots--they tested good--dropped them in (Dave marked them for treb, mid, and bass) and fired it up.

This time, the treble and the mid controls worked fine, and bass control was doing nothing.

y3exvgGm_o.jpg


This was the point I went online to find a schematic because this is a "printed circus board" based amp, and the traces are on the underside of the board. If I could see signal flow, I could troubleshoot the thing. But no dice--there is no schematic available. And there is no way I'm pulling 50 connections to remove the board and have a peek under her skirts.

So I got busy looking for a poor solder connection, etc., on the topside of the board. I found four resistors that looked like they had been already replaced following the initial build, and all but one had good, clean solder connections. The one bad solder joint was a pretty bad crusty blob on a 1/2-watt resistor in the power section. This was nowhere near the tone circuit, but I fixed that anyway.

sLwgnUDO_o.jpg


At this point, I was stuck because no schematic. So I put the original pots back in and fired it up, expecting it to revert to the original complaint.

But everything worked fine! What the heck? I told my pal that it's working fine, until it doesn't all over again; the amp is unreliable and it probably has a bad ground somewhere in the tone section.

That is when he mentioned this was the second Friedman Runt he's had, because the first one went back with inop tone controls on the clean channel. WHAT? Holy smokes.

I asked him to call his guy at Chuck Levin's and see if he can bring this one back for an exchange. He did, and lucky for him they have a few in stock. So it's going back. Perhaps the third time's the charm.

This is really puzzling to me because having owned a killer sounding and trouble-free Friedman Pink Taco for several years, I cannot understand the pattern of failures with this one...and the previous one.
 

Phrygian77

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Where are they assembled?

I ditched a Blackstar HT Stage 60 someone sent me not long ago because of faulty bias circuit. All of the SMD on the board plus the complexity just made it a nearly impossible job to track down.
 

Peegoo

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Pretty sure they're made in the US...but these PC based amps are their down-market products, which allow mere mortals to get Friedman goodness for less than half of what his hand-wired amps go for.
 

chas.wahl

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Terrific design is great, but without quality execution, it's pointless. The story of my life as an architect. (Of course, sometimes crappy execution can't be helped because of incompetent design, but I doubt that's the case here.

The old saw is "I want it good, cheap and fast" response being "go home, think about it, pick two and get back to me". This can also be described as a triangle with quality, cost and speed as the apices -- choose where you want to be in that triangle.
 

dan40

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The factory in California (Boutique Amp Distribution) that builds stuff for Friedman, Wampler, Tone King, Bogner and others had a fire last year that messed up production on Friedman amps for a bit. Dave has also complained of quality control issues with tubes and other components ever since you know what started to affect the World. It's possible that this batch of amps were built during the time they were getting back on their feet after the fire and the lock downs ending. Hopefully the next amp will be from a newer batch.
 

Phrygian77

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Replace the MosFets, re bias and that is it, a working Black Star.

I think this was an issue of the relay controlled bias not enabling, so basically like -90Vdc bias on the EL34s. No bias or balance controls did anything. I didn't get much further than that. I know that part of the circuit is FET controlled. Are you saying that's where the problem was?
 

loudboy

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I've had more problems with high-end, small-run stuff than cheaper, mass-produced gear.

I had a Soundelux mic that shipped with the wrong value cap on the board, and it was not a large board. A few other similar problems with expensive pres and recording gear.
 

Jon Snell

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I think this was an issue of the relay controlled bias not enabling, so basically like -90Vdc bias on the EL34s. No bias or balance controls did anything. I didn't get much further than that. I know that part of the circuit is FET controlled. Are you saying that's where the problem was?
Those are the cause of the issue. In standby, the bias goes heavily negative to stop conducton, (a stupid idea), the faulty FETs can damage the switching circuit.
Don't forget, if a speaker jack has a damaged contact, you will get the same result!
 

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NTC

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For the original problem, my guess is that the issue is at the connectors on the pot harnesses. They may not gave been inserted completely (unlikely, really), the pins could have been crimped badly, and the wire may actually be broken inside the connector. Could also be something like corrosion on the pins - any idea what the pins are plated with? Probably not gold. If the are silver plated, they will be a continuous source of trouble.
 

Jon Snell

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For the original problem, my guess is that the issue is at the connectors on the pot harnesses. They may not gave been inserted completely (unlikely, really), the pins could have been crimped badly, and the wire may actually be broken inside the connector. Could also be something like corrosion on the pins - any idea what the pins are plated with? Probably not gold. If the are silver plated, they will be a continuous source of trouble.
Usually Nickle (N). If Cliff sockets, they don't like a damp atmosphere.
 

11 Gauge

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For the original problem, my guess is that the issue is at the connectors on the pot harnesses. They may not gave been inserted completely (unlikely, really), the pins could have been crimped badly, and the wire may actually be broken inside the connector. Could also be something like corrosion on the pins - any idea what the pins are plated with? Probably not gold. If the are silver plated, they will be a continuous source of trouble.

This is probably what I'd consider the top suspect, too. I wouldn't be surprised if there were cold solder joints on some of the connector solder pins, or maybe some kind of crud around them (although not necessarily corrosion) causing issues. Since that's all hidden on the underside of the PCB, there's no way to know w/o yanking it.

If the amp uses the typical T/M/B type of tone stack, which I would guess is very likely, you could check for continuity between pot lugs and the 3 caps and resistor that are likely part of the tone stack (I think I see them all on the PCB in the pic provided). And for the mid pot, it would simply be a matter of checking for continuity to ground between the appropriate pot lug and either the chassis itself, or a known ground on the PCB (like the negative end of a cathode bypass capacitor, if it has one).
 
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