Another Red Flag On The Ampeg PF-500.....

[will33]

But have the SVT revisions been because of design/componet flaws that affect reliability, (as in the PF's), or have they been just additions as in a XLR outs, master volume controls?

Other than the switch from 6146B power tubes to 6550's, which I think was more about availability/cost and not reliability....I just plain don't know.

Adding master volume, color/style changes, DI's etc. would all be revisions that have nothing to do with reliability.

 

[B-string]

Define "revision" for the "SVT". Are we talking just the original design or to include the SVT II, SVT II PRO, CL, VR, SVT's that were convoluted with SS power amps. It becomes more about badging a new model to sell with a badge than "revisions"? Revisions are changes to one product model. Is a re-issue as in the case of the CL a "revision", or it is a "re-issue" with the necessary changes for parts availability and whatever feature set the new producer wishes to "update" with.

 

[will33]

I was just thinking of the regular SVT 300 watt tube amp. 2-Pro's, hybrids, etc. I consider different models. Although from the original to the CL, etc., I'd consider the same model, with revisions, or more like additions really, like master vol., DI, color changes, etc. I suppose the VR or Heritage would be "subtractions", or "reverse revisions" going back to the earlier models, like the color/style, removing the master vol., etc.

 

[JimmyM]

The original SVT switched from having a tube relay to a solid state relay almost immediately because if the tube went out, so did the whole amp. The 6146b's were replaced with 6550's in the first year because of the inventor seeing Keith Richards play so hard that he caused the filaments to glow cherry red and the glow would hop from tube to tube, plus they decided that having the power supplied through a little wire with a cap on it that the user could electrocute him/herself with if not careful also wasn't the best idea ever.

So anyone's argument that the SVT was revised for any other reason besides design flaws is rejected. Holy crap, you people! You complain when the PF500 doesn't work, and then you complain that they fixed it. How ridiculous is that? I expect that kind of nonsense from arai, who's still angry that I busted TC's balls about their wattage claims, but the rest of you?

 

[Bowe]

Since it came out in what..........1968?

The PF-500 has "probably" had as many revisions (11 so far) in the few years since it hit the market as the SVT has had in the 45 years of it's release.

With the SVT, it's revisions has been additional features added to a almost, originally perfect design, (XLR outs, master volume, bias controls, ect.)

With the PF-500's it's been changes to design/componet flaws.

.......

But have the SVT revisions been because of design/componet flaws that affect reliability, (as in the PF's), or have they been just additions as in a XLR outs, master volume controls?

And how do you know that the ECs on the PF are due to 'design flaws' - I've read the list and most of them have nothing to do with the published 'design flaws.'

If you don't like the PF line that is your choice but don't just make up stuff.

 

[Bowe]

The original SVT switched from having a tube relay to a solid state relay almost immediately because if the tube went out, so did the whole amp. The 6146b's were replaced with 6550's in the first year because of the inventor seeing Keith Richards play so hard that he caused the filaments to glow cherry red and the glow would hop from tube to tube, plus they decided that having the power supplied through a little wire with a cap on it that the user could electrocute him/herself with if not careful also wasn't the best idea ever.

So anyone's argument that the SVT was revised for any other reason besides design flaws is rejected. Holy crap, you people! You complain when the PF500 doesn't work, and then you complain that they fixed it. How ridiculous is that? I expect that kind of nonsense from arai, who's still angry that I busted TC's balls about their wattage claims, but the rest of you?

+1000
Plus the circuit in the SVT is vastly simpler and was an extension of the design they'd been using for 20+ years before.

 

[WretchedExcess]

One reason for going away from 6146B is because those tubes are a lot more dangerous than a 6550.

On a conventional tube amp there are two layers of safety between the user and the high voltages that can kill them: a) the cover screen, and b) the box chassis. With most guitar & bass amps you can remove the cover screen and not be exposed to anything dangerous because the high voltage wires are contained within the box chassis. Amps like the Tweed/BF/SF Fenders don't even have a cover screen. It's good enough that all of the high voltage wiring is self-contained inside of the metal box chassis.

The original SVT wasn't designed that way. In the original SVT the 6146B have got the anode electrode coming out of the top of the tube envelope, which has a little non-conductive cap snapped onto it, and a wire running into the boxed chassis. Those 6 plate electrodes and the 6 wires running into the chassis carry ~700 VDC and lots of amps. Enough to kill you.

I know a professional full-time amp builder and amp tech who's been in the business for decades. Bruce Collins at Mission Amps is missing the tip of a finger because of that 700VDC that's on those six wires that are "loose" in the external chassis of the original type SVT.

The original SVT design was definitely one that carries more risk to work on than the later designs. I won't own one, and I won't work on one either. I just don't like to be around them.

 

[shoot-r]

The original SVT switched from having a tube relay to a solid state relay almost immediately because if the tube went out, so did the whole amp. The 6146b's were replaced with 6550's in the first year because of the inventor seeing Keith Richards play so hard that he caused the filaments to glow cherry red and the glow would hop from tube to tube, plus they decided that having the power supplied through a little wire with a cap on it that the user could electrocute him/herself with if not careful also wasn't the best idea ever.

So anyone's argument that the SVT was revised for any other reason besides design flaws is rejected. Holy crap, you people! You complain when the PF500 doesn't work, and then you complain that they fixed it. How ridiculous is that? I expect that kind of nonsense from arai, who's still angry that I busted TC's balls about their wattage claims, but the rest of you?

Good information about the early SVT, mine was (I believe a 69 with 6550's)...

As to "my" complaint against Ampeg's PF-500's...

My beef with Ampeg is that none...no...nada...not any, consideration was given to repairing these units (at the owners expense) when the amp was out of warranty.

 

[B-string]

I certainly am not "capping" on the all tube SVT's? I didn't even bring them into the discussion, in fact trying to pointing out that they have no real bearing on this discussion.

 

[B-string]

One reason for going away from 6146B is because those tubes are a lot more dangerous than a 6550.

On a conventional tube amp there are two layers of safety between the user and the high voltages that can kill them: a) the cover screen, and b) the box chassis. With most guitar & bass amps you can remove the cover screen and not be exposed to anything dangerous because the high voltage wires are contained within the box chassis. Amps like the Tweed/BF/SF Fenders don't even have a cover screen. It's good enough that all of the high voltage wiring is self-contained inside of the metal box chassis.

The original SVT wasn't designed that way. In the original SVT the 6146B have got the anode electrode coming out of the top of the tube envelope, which has a little non-conductive cap snapped onto it, and a wire running into the boxed chassis. Those 6 plate electrodes and the 6 wires running into the chassis carry ~700 VDC and lots of amps. Enough to kill you.

I know a professional full-time amp builder and amp tech who's been in the business for decades. Bruce Collins at Mission Amps is missing the tip of a finger because of that 700VDC that's on those six wires that are "loose" in the external chassis of the original type SVT.

The original SVT design was definitely one that carries more risk to work on than the later designs. I won't own one, and I won't work on one either. I just don't like to be around them.

They don't bother me that much, but then I used to work with commercial AM/FM transmitters. Anode voltages of several thousand volts and delta Y 408 vac supplies.

 

[shoot-r]

And how do you know that the ECs on the PF are due to 'design flaws' - I've read the list and most of them have nothing to do with the published 'design flaws.'

If you don't like the PF line that is your choice but don't just make up stuff.

Not an electronic tech and never claimed to be, but at 11 revisions to the PF-500 in the couple of years of it's being on the market, all to do with reliability, I'd say there's a design/componet flaw of some kind.

I liked the PF-500's enough to own two of em'.......they BOTH burnt out.......kinda hard not to be upset!








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[Bitterdale]

Not an electronic tech and never claimed to be, but at 11 revisions to the PF-500 in the couple of years of it's being on the market, all to do with reliability, I'd say there's a design/componet flaw of some kind.

I liked the PF-500's enough to try two of em'.......they BOTH burnt out.......kinda hard not to be upset!

Where are you getting this information from?

 

[P Town]

And how do you know that the ECs on the PF are due to 'design flaws' - I've read the list and most of them have nothing to do with the published 'design flaws.'

If you don't like the PF line that is your choice but don't just make up stuff.

Bowe.
If you know specifically what the change history is, would you be able to share it with us.
I would like to know as many details as possible.

Thanks.

 

[WretchedExcess]

They don't bother me that much, but then I used to work with commercial AM/FM transmitters. Anode voltages of several thousand volts and delta Y 408 vac supplies.

The problem isn't so much with dealing with those kinds of voltages -- I can do it if need be, but to me it's just not worth it. The 6550 type of SVT is a fine amp, and the 6146B type of SVT is not any better. It offers no advantage to compensate for the added risk in working on one, so I don't own one.

When it comes to servicing them, I don't think that the musical instrument marketplace really understands the type of risk that that sort of amp provides, to the point that a musician doesn't fully appreciate the situation. The result is that there is no added reimbursement that is commensurate with the added risk for working on that type of gear. for that reason I prefer to just send that work elsewhere. Some guys think it's fun to work on that kind of stuff, so I let them take on added risk for no extra pay. I'm lucky that I can afford to turn work away on a whim.

 

[shoot-r]

Where are you getting this information from?

Ampeg's service tech, Analog Outfitter's, Champaign Illinois.
Ampeg PF-500's Main Board is now at Revision "J".
It's my understanding, first unit is 0, then A, B, C, D, E, F, G, H, I, J.
10 + 1 = 11 revisions.

If I'm reading the post right, Will33 confirms this at post 469.





.......

 

[B-string]

That is certainly fine, I am just one of the foolish than are not bothered by it . It was not a "safe" consumer design but at the time uncaged exposed anode Horizontal output tubes were still commonplace. Many consumer safety regulations have since been put in place to protect the foolish consumer who will put body parts where they should be.

 

[Bowe]

Not an electronic tech and never claimed to be, but at 11 revisions to the PF-500 in the couple of years of it's being on the market, all to do with reliability, I'd say there's a design/componet flaw of some kind.

I liked the PF-500's enough to try two of em'.......they BOTH burnt out.......kinda hard not to be upset!

Part 2 - you have that right - but is the cause known? Is the rev level known?

Part 1 - don't just make stuff up
The big changes were finished in Feb. 2012 (rev. E) some 13 months after it was released (and how long did it take to get the SVT right??). And at the letter rev level there have been total of 6 changes (D, E, F, G, H, J) and H was a change to the connector for the pre-amp and J seems to be a component provision issue, not reliability related.

My rev. G, shipped Jun 2013, has functioned flawlessly.

EDIT: rev. C was issued 3 months before the unit was shown at NAMM 2011
reEDIT: there was not a rev between H and J

 

[shoot-r]

Many consumer safety regulations have since been put in place to protect the foolish consumer who will put body parts where they shouldn't be.

From my day job, from the other night...the story I could tell you about this topic.......

 

[Bowe]

That is certainly fine, I am just one of the foolish than are not bothered by it . It was not a "safe" consumer design but at the time uncaged exposed anode Horizontal output tubes were still commonplace. Many consumer safety regulations have since been put in place to protect the foolish consumer who will put body parts where they should be.

+1
And I'd been in the broadcast engineering field for almost 20 years.

 

[arai]

As to "my" complaint against Ampeg's PF-500's...

My beef with Ampeg is that none...no...nada...not any, consideration was given to repairing these units (at the owners expense) when the amp was out of warranty.

Agreed.
It's time they came to the party and show people who have owned dud pf amps some respect. It would do Ampegs reputation wonders if they treated the, well documented, problematic revisions as a write off and replace those amps pro bono