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Ampeg Portaflex bad circuit board (PCB)?

Discussion in 'Amps and Cabs [BG]' started by espace, Jan 23, 2017.

  1. espace


    May 27, 2008
    I can't seem to find some info I saw in a thread here.

    It gave the year of the new Portaflex heads (Edit: only the PF-500) when Ampeg resolved the issues that they had, and how to identify the fixed model by serial number.

    Also, I'm not positive if it was just the PCB or some other issue.

    Does anyone have any info on this?
    Last edited: Jan 26, 2017
  2. Crater


    Oct 12, 2011
    Dallas, TX area
    The "Portaflex" name covers a lot of different Ampeg products, from the 1960s until the current day. Is your question about the notorious PF-500 amp head? Search by a specific model number.
  3. espace


    May 27, 2008
    Sorry, yes the modern heads, I edited my post to show this. I searched for these models and can't find the thread that has this information.
  4. Crater


    Oct 12, 2011
    Dallas, TX area
    It's really only the PF-500 that has the bad reputation. The early versions of this amp (I own one of these, by the way) were known for "cutting out" on high volume peaks. If you open the amp and look at the main circuit board, there should be a "rev" (revision) number, or rather a letter. My PF-500 is a rev. C board, one of the "bad ones" supposedly. New amps are at rev. J or something.

    You can purchase a replacement power amp mainboard at THIS LINK.
  5. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    On each schematic, there is a list of revisions for that particular model. A revision does not mean that there was an issue. It is a change that can relate to a substituted a part, added or took away a component, etc. There are service bulletins that deal with specific repairs.

    I've never seen a summary of issues resolved for all models.

    What are you specifically looking for?
  6. espace


    May 27, 2008
    Thanks, didn't know it's only the PF-500 that has that issue.

    Have you not had a problem with it, or do you just not use it at high volume?

    I did know they revised the PCB. I was wondering what year they did, so it can be identified without opening the amp.

    Thanks for the info on how to buy a new board, but I'm just trying to identify the revised models by the SN on the outside of the amp so I can buy a used one without getting a lemon.

    Looking at my 1st post, this isn't so clear, so I'll fix that.
  7. espace


    May 27, 2008
    There is a known issue with these heads. I couldn't remember what it was. I though it was all of the PF-X00 class-D series heads, but I guess it was just the PF-500.

    I'm trying to identify the revised models by their serial number.
  8. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Although you don't want to do it, opening the amp will allow you to determine the board revision number. It's silk screened on the board. Once you have that, you can go from there.

    The PF350/500/800 are all different designs. There is no single change in the power amp that applies to all models.
  9. Crater


    Oct 12, 2011
    Dallas, TX area
    There's so many threads on this it's difficult to search. Basically, the issue was the amp would "cut out" and go into protect mode on loud transients. Usually cycling the power resets the protection circuit and you can keep playing, but some amps flat-out died on people. A class-D amplifier, unlike a class A/B amp, cannot be driven beyond it's power rating. Class-D amps must have protection circuits to protect the power MOSFET transistors, and if try to overdrive the power amp, the protection circuit shuts it down. I think other class-D amps deal with this problem by having an aggressive 'brick wall' limiter before the power amp stage to keep it from going into protect mode.
    Pederbas likes this.
  10. espace


    May 27, 2008
    Well, this is Ampeg's (Loud Technologies) response to me:

    Hi Eric,
    That is not true. The PF800 has been as solid as a rock. The PF500, while having some issues (usually caused by customer abuse), still has a quite low failure rate overall. There have not been any major revisions to the PF500.
    All the best,
    [email protected]
    1(800)258-6883 Ext. 1633
    Loud Technologies Inc.

    They seem to deny it really had any issues, and blame the customer, then insinuate it was never "fixed" with a Rev.

    I'm really looking for a used PF-800, but might have to settle for a PF-500 since they seem to be more available on the used market. And cheaper.

    I guess it's impractical for me to open the head before I buy a used one to check for the Rev. But, if the owner knows or is willing to check, what Rev should I be looking for on the PF-500?
  11. okcrum

    okcrum in your chest

    Oct 5, 2009
    Verde Valley, AZ
    RIP Dark Horse strings
    Check for Rev. D or higher, which happened 4-5 years ago now.
  12. blubass


    Aug 3, 2007
    Modesto Ca
    Current: Blackstar, DR strings, Nady. Previous endorsements with: GK, Rotosound, Ernie Ball, Cleartone, EMG, Dean, Dava Picks, Rebel Straps, Dickies
    They didn't deny anything, you just copied the response.
    They said it had some issues.
    They did say it was usually due to customer error.

    That is entirely plausible. Anyone on this forum can see the many threads about where to set the gain, how to understand Impedance, hooking up 15 pedals in front of an amp with no clue how to set them.... etc. We're only a very small portion of the bass playing community; who knows what other stuff goes on that we never hear about.

    Have you seen some of the amps on Craigslist or being brought into music stores for trade in? It's a high percentage of misused and mistreated garbage.

    Then, they told you the failure rate was still quite low. That is also plausible. They have exact numbers of total production vs. What's been returned for warranty work, or parts sent out.

    They went on to say that there were no major revisions. They didn't insinuate anything. Why would a company release a faulty amplifier, then lose money hand over fist on free warranty work, and not wise up and fix the issue? That's bad business.

    So in summary, they didn't have major issues with the PF500. They had several issues, which probably didn't require major revisions to remedy.

    Did we read the same email?
    Last edited: Jan 26, 2017
    Bass 45 likes this.
  13. Jay Corwin

    Jay Corwin Supporting Member

    Jan 29, 2008
    Sanborn, NY
    The idea of what a major issue is defined as, isn't going to be consistent between the customer and the manufacturer. For example, if some using a PF500 on a gig had it fault out into protection mode during a set - BOOM!.....major issue from them. However the remedy (and I'm only speculating) could have been a very small "fix" if you will to the PCB or protection scheme in general from Ampeg. Sometimes the cause of a problem isn't that difficult to deal with, while the result of that problem can be. This could account for them saying that no major revisions have been made to the board.

    I will say that they probably shouldn't include that line about customer abuse in their response though. Poorly chosen words for a CS department.
  14. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Since you are in the process of buying an amp, I doubt that a seller would be willing to open it up and check for a revision number. Even if you had the revision, you don't know how the amp has been used, if it was serviced, etc. Most people wouldn't know what to look for when it comes to any changed parts.

    I know that a new amp is expensive, the PF500 sells for $400. I would never buy a solid state amp that didn't come with a warranty unless I knew the seller and trusted them. Sometimes a gamble is worth it if it is a great deal and you can afford to write it off if an issue arises.

    You can date the amp from the serial number. The amp has been on the market for a number of years. A lot have been sold, any issues would have been resolved early in the product cycle. You'd think that a three year old model or newer would be a safe bet.
    Last edited: Jan 26, 2017
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    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

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