Ampeg PF350/500 Part VI

[dkelley]

I can't say I know the answers but there have been a number of changes to the circuit in the PF500, including adding snubbers to the finals (10/2011), fixing PWM freq. (07/2012), changing a handful of passives (2011-2013), changing a couple diodes in the PSU (02/2013), and the last change was to an opamp (06/2013), so they are making changes that can improve the reliability of the product. I don't think that I let out any secrets with this posting.

The PF500 that I received in June doesn't have the new opamp but has all the other changes and runs just fine.

Cool. Any idea if similar things are being done to the pf350? I'm going to assume diodes in the psu as an obvious culprit, but even an opamp dying will still being things to a stark silence of course. Passive sections too although I'd be more surprised to find that to be the cause of these sudden deaths.

 

[Bowe]

To get the prints I simply sent LOUD CS an email asking for them, they sent a non-disclosure/its-my-fault-if-I-do-something-stupid agreement and then I got them. I should say I did have to give the S/N of the amp so they knew that I am an owner.

 

[P Town]

It would be useful to have all the ECs, and drawing revision numbers documented.

Wondering if we can all post PDFs of the various schematics Loud provided to us owners as a way to see the progression of changes.

We may be able to get an understanding of what the various failures have been, and be able to upgrade, or more easily repair out of warranty units by knowing what changes were made.

 

[Jim Carr]

This is a cross/re-post from the PF-500 thread. Consider it a twisted cry for help.
How am I going to sell this thing???

Sold my PF-350 after two months of ownership. Used it a dozen times. Worked fine. Even sounded good, though not LOUD (the good kind).

New owner is having problems after using it for one rehearsal and one gig—crackling, distortion, etc. I'm refunding his money.

I've had problems with every brand of amp I've purchased in the last 8 years, except my Crest CA6—so I am not shocked. HOWEVER, I bought ALL of THEM used.

The PF-350 was an exception. Bought it new at Dallas Zoo Music—a local chain. It's going back to Ampeg.

Now where is that blasted receipt???

 

[Bowe]

Bowe,

What are the Rev numbers, and last date of ECs of the preamp board, and main board schematics that you are looking at for the PF-500?

Mine are: preamp rev: B00, last EC date: 6/30/10, and main board rev: C03, last EC date: 6/20/11.

Any reason we can't share schematics of failed, vs non-failing versions to see if we can identify likely failure modes?

Maybe owners could be proactive with upgrades, or having repair parts on hand if we can understand what the common problems are, and what Loud has done to improve reliability on subsequent revisions.

Mine is quite a bit newer:
Preamp is the same rev. B00 EC 6/30/2010
Main board is rev. J00 EC 4/23/2013 (and J01 is a BOM change ...) the board itself is silkscreened as a rev. G__

I confirmed the rev. by reviewing the changes and my board has them. There is no notation on the board to ID the rev. level other than the silkscreen.

According to the print I have the latest is rev. J02 EC 06/04/2013 and if mine was that rev. it would've been a miracle since it was shipped from LOUD on the same day!!!

 

[Bowe]

Cool. Any idea if similar things are being done to the pf350? I'm going to assume diodes in the psu as an obvious culprit, but even an opamp dying will still being things to a stark silence of course. Passive sections too although I'd be more surprised to find that to be the cause of these sudden deaths.

I don't think the diodes that were changed would be the culprit, but there have been at least mention of a bad solder joint and one regarding MOSFET failure. The $64000 question is which MOSFETs took it? In many of the big switching amplifiers I've dealt with it was a MOSFET that collapsed causing the failure (not Ampeg BTW) and these were in the HV-PSU and the PA. In either case it would effectively kill the power amp and not affect the low-volt sections.

I can say that the wave soldering was a bit skimpy but adequate on my unit. The solder didn't make it 100% of the way up through the holes (I'd say about 85% on the low ones but the underside was complete and clean) so there is, as always, the possibility of some solder defects that are passing QC. I also will admit mine failed the rattle test on arrival, there was a few inches of cut off zip tie still in the chassis that should have been removed before the case was sealed. Other than the HV transformers, the heavier parts and the parts more likely to move were all siliconed to the board.

I'll post pix if desired, I even took close ups of most of the main board, including the bottom so if something happens I know what it was supposed to look like.

 

[B-string]

Minimal solder is not a bad thing as non-lead solder is subject to growing "tin whiskers" that causes all kinds of trouble. Shorted or otherwise failed laptop motherboards is prominent example of tin-whiskers destructive nature.

 

[okcrum]

I loaned my 2nd rig (PF500 + 2xB115E) to a buddy whose MB800 rig died Sat. afternoon. Luckily our gigs, my house, and the venue where the B115Es were were all within ten minutes or so of each other.

He was happy enough with it that he's thinking of getting one.

 

[okcrum]

I don't think the diodes that were changed would be the culprit, but there have been at least mention of a bad solder joint and one regarding MOSFET failure. The $64000 question is which MOSFETs took it? In many of the big switching amplifiers I've dealt with it was a MOSFET that collapsed causing the failure (not Ampeg BTW) and these were in the HV-PSU and the PA. In either case it would effectively kill the power amp and not affect the low-volt sections.

Agreed. The first two changes Ampeg did were definitely for the PA MOSFETs. Those can fail from inductive spikes (like the HV-PSU MOSFETs), hence the snubber change. The other way they can fail is via a commutation failure, when you get two MOSFETs on in the same half bridge, shorting the power supply. The second change seems to address that. Both changes would help with parts right at the tolerance limits for breakdown voltage and switching time.

I'd guess the outright fail rate dropped considerably from those two changes alone.

 

[Woodstockz]

I can't say I know the answers but there have been a number of changes to the circuit in the PF500, including adding snubbers to the finals (10/2011), fixing PWM freq. (07/2012), changing a handful of passives (2011-2013), changing a couple diodes in the PSU (02/2013), and the last change was to an opamp (06/2013), so they are making changes that can improve the reliability of the product. I don't think that I let out any secrets with this posting.

The PF500 that I received in June doesn't have the new opamp but has all the other changes and runs just fine.

Do you know which board revisions had which changes. The board revision letters don't show the dates.

For example, which boards had the snubbers?

It would be good if we had more info on these changes...

 

[Woodstockz]

...

Wondering if we can all post PDFs of the various schematics Loud provided to us owners as a way to see the progression of changes.

...

When you get a schematic from Ampeg, you "agree to not redistribute".

 

[P Town]

I would like to officially invite Loud to respond to technical questions regarding design revisions to the PF-500 amplifiers so that owners of out of warranty units may be able to ensure that we are able to keep our amplifiers up to date, and operating properly.

 

[P Town]

When you get a schematic from Ampeg, you "agree to not redistribute".

I figured as much. I only remembered that I promised to not electrocute myself, and to not sue them after having done so.

Since I have the schematic for the amp I own (for which I provided a serial number to obtain), I could probably get the latest schematic by providing the serial number for a brand new, recently manufactured amplifier found in the show room of my local Ampeg retailer.

Problem solved.

Sorry to have to be devious.

 

[Bowe]

I figured as much. I only remembered that I promised to not electrocute myself, and to not sue them after having done so.

Since I have the schematic for the amp I own (for which I provided a serial number to obtain), I could probably get the latest schematic by providing the serial number for a brand new, recently manufactured amplifier found in the show room of my local Ampeg retailer.

Problem solved.

Sorry to have to be devious.

Not that this would help you that much but LOUD doesn't seem to issue the older schematics, just the current one, as my amp was shipped from LOUD the same day as the last EC was written, well the last EC on my print that is.

The pace of change is interesting to note as there were 3 ECs in 2010, 4 in 2011, 5 in 2012, and 5 in the first half of 2013. There was only 1 change in the latter half of 2012 (in December when they issued the rev. G board) and the snubbers and buffers were rev. D and rev. E respectively. At least one of the 2013 changes was a BOM change and another 1 or 2 may be supply issues, whereas 2011 and 2012 appear to be substantive changes.

I suppose that I may have a rev. G01, I cannot confirm the rev. H00 (a connector change - maybe supplier/BOM change) but the cap change from J00 seems to be present (same value cap that is in the print) and I know I don't have the opamp change for rev. J02.

Here is the crux of the biscuit from the Ampeg agreement:

If you are absolutely sure that you are qualified to safely do this type of repair and also agree to not redistribute without the prior written consent of Loud Technologies, Inc., we will grant one set of schematics if available.

To keep within the agreement I have not disclosed any details that would compromise the IP contained in the prints.

My interior details are:

 

[254 stringer]

Not that this would help you that much but LOUD doesn't seem to issue the older schematics, just the current one, as my amp was shipped from LOUD the same day as the last EC was written, well the last EC on my print that is.

The pace of change is interesting to note as there were 3 ECs in 2010, 4 in 2011, 5 in 2012, and 5 in the first half of 2013. There was only 1 change in the latter half of 2012 (in December when they issued the rev. G board) and the snubbers and buffers were rev. D and rev. E respectively. At least one of the 2013 changes was a BOM change and another 1 or 2 may be supply issues, whereas 2011 and 2012 appear to be substantive changes.

I suppose that I may have a rev. G01, I cannot confirm the rev. H00 (a connector change - maybe supplier/BOM change) but the cap change from J00 seems to be present (same value cap that is in the print) and I know I don't have the opamp change for rev. J02.

Here is the crux of the biscuit from the Ampeg agreement:


To keep within the agreement I have not disclosed any details that would compromise the IP contained in the prints.

My interior details are:
View attachment 361483

I didn't look underneath the main board but here are the ones I could see. I bought this a couple of months ago and it has worked perfect. I have pushed it hard into a 4 ohm load and couldn't get it to cut out before the speakers started to fart out.

 

[bassguppy]

Rebate from Ampeg for the PF-500, PF-800, PF-115HE, & PF-410HE.


http://www.ampeg.com/2012/wp-content/uploadfix//2013/08/2013-Q3-Portaflex-Coupon.pdf

 

[MarkH_129]

Ok. It happened. I got it in June (PF-500) and it just fizzed out on me. Yeah, it bugs me. Now Im wondering how long it will be before I get it back. I've been playing on it almost every day. Bummer.

 

[Bowe]

I didn't look underneath the main board but here are the ones I could see. I bought this a couple of months ago and it has worked perfect. I have pushed it hard into a 4 ohm load and couldn't get it to cut out before the speakers started to fart out.View attachment 361690View attachment 361691

I find it interesting that you picked up a rev. D "a couple months ago" as the EC is dated 10/29/2011 and the EC date for rev. E is 02/21/2012 which works out to four months of production over a year ago. It's looking like there are a number of the older revs still on store shelves.

Ok. It happened. I got it in June (PF-500) and it just fizzed out on me. Yeah, it bugs me. Now Im wondering how long it will be before I get it back. I've been playing on it almost every day. Bummer.

I think it would be a good idea to pop it open when you get it back to check on the rev. Post a pic of the rev here afterward I'd like to see what the changed C35 in rev. J looks like, assuming they stick a rev. J or H main board in it. All the pics I've seen have the same type cap for C35 (the green poly by the silk screened rev code) and the EC only says it changed, but nothing about from or any other specs than value.

 

[254 stringer]

I find it interesting that you picked up a rev. D "a couple months ago" as the EC is dated 10/29/2011 and the EC date for rev. E is 02/21/2012 which works out to four months of production over a year ago. It's looking like there are a number of the older revs still on store shelves.



I think it would be a good idea to pop it open when you get it back to check on the rev. Post a pic of the rev here afterward I'd like to see what the changed C35 in rev. J looks like, assuming they stick a rev. J or H main board in it. All the pics I've seen have the same type cap for C35 (the green poly by the silk screened rev code) and the EC only says it changed, but nothing about from or any other specs than value.

A couple of months is a stretch I actually got it in May when they had the rebates on the cabs. I was hoping it was a newer build but I guess not. At least I still have a year and eight months of warranty left if it goes out.

 

[Lync]

Last night I experienced the "cut-out" problem. Here's what happened and I what did to make it not happen (and it worked).

I had 2 gigs in one day and used the PF500 into my Genz 212 neox for both. First gig was a loud modern country band where I predominately used my upright. No issues...master & gain at 12:30...sounded great for the full 3-1/2 hour gig.

Then my second band is a shred/80's metal band. We were opening up for a Kiss tribute. The guitarist in the band has a Soldano SLO100 into a 4x12 cab (LOUD). So I turned the PF500 up to about 1am. The drummer needed more so I turned up the master to 2 o'clock. Started the soundcheck and the amp cut out on a few notes.

So...I adjusted the gain and brought that down to about 11ish (it was at 1230). The amp worked, but not loud enough. So I brought the master up to 2:30.

Worked great and never cut out again. So my cut out was definitely the protection just kicking in from using a hot bass (MM Stingray) at the first gain setting. Nothing was actually wrong with the amp.

Just something to check out if this happens to you.