I have a Lab Gruppen fp6400 that was repaired about 6 years ago, but sat on the shelf for maybe 5 years.
After the repair it worked fine, but I recently put it back in service and it has a very odd problem: It works perfectly for maybe 5-10 minutes, then I hear a small pop, and it goes to maybe 2/3 or 1/2 total power.
it still works, sounds fine, and makes no noise, just lower output, and will then run like that all day.
Does this ring any bells? I'm think maybe one of the supply caps went bad, yes?
Anything else it might be, that a guy with basic electronics skills could deal with?
thx.
After the repair it worked fine, but I recently put it back in service and it has a very odd problem: It works perfectly for maybe 5-10 minutes, then I hear a small pop, and it goes to maybe 2/3 or 1/2 total power.
it still works, sounds fine, and makes no noise, just lower output, and will then run like that all day.
Does this ring any bells? I'm think maybe one of the supply caps went bad, yes?
Anything else it might be, that a guy with basic electronics skills could deal with?
thx.
Only by this posting I came to know of a "Lab Gruppen". Had to look at the Internet to understand it is a Swedish Volvo with a Lamborghini (not the tractor) engine. What do I mean by that? I mean a sturdy and orderly designed mechanical construction with an electronics that due to complexity, parts-count and parts-stress is likely to be unreliable in use.
And, dreadful in repair.
You mention it has been repaired years back, then put aside for years and only now brought back to use with a problem. Not much of a reliability record.
Anyway, we can try to see if we can figure out what is wrong.
From what you describe, it sounds like the amplifier (wrongly) detects an overload situation, probably thermal overload, and reduces the volume to cool down the amplifier. Have you knowledge about where the protection circuit is located in the chassis and where it interfaces with the amplifier circuit?
And, dreadful in repair.
You mention it has been repaired years back, then put aside for years and only now brought back to use with a problem. Not much of a reliability record.
Anyway, we can try to see if we can figure out what is wrong.
From what you describe, it sounds like the amplifier (wrongly) detects an overload situation, probably thermal overload, and reduces the volume to cool down the amplifier. Have you knowledge about where the protection circuit is located in the chassis and where it interfaces with the amplifier circuit?
Yeah, that must be why all those European touring companies use them.
Thx, that sounds somewhat likely. I have no idea about that circuit, as I can't obtain a schematic nor service manual. I was hoping it might sound like some simple component failure (a leaking cap or whatever) but I guess not.
Time to send it out.
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Hi
i just google your amp.....heavy mechanical construction and compress build....
Maybe its a nice try to start with seperate the left channel from R channel testing.
e.g. disconnect the left channel as good as possible completely. is the strange pop still there? then try the R-Channel.
...so please be aware of the hazardous psu part --> there is more voltage as you might think !-if there is a SMPS...--up to 400V
discharging a cap with 1 HAND is recommended !!!
chris
i just google your amp.....heavy mechanical construction and compress build.
...Maybe its a nice try to start with seperate the left channel from R channel testing.
e.g. disconnect the left channel as good as possible completely. is the strange pop still there? then try the R-Channel.
...so please be aware of the hazardous psu part --> there is more voltage as you might think !-if there is a SMPS...--up to 400V
discharging a cap with 1 HAND is recommended !!!
chris
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...mybe here is something...
so you can start with a searching effort
Index of /ciasteczkowypotwor/SM_scena/LabGruppen
so you can start with a searching effort
Index of /ciasteczkowypotwor/SM_scena/LabGruppen
...mybe here is something...
so you can start with a searching effort
Index of /ciasteczkowypotwor/SM_scena/LabGruppen
Super job by Chris as usual!
I found an FP6400 service manual with this link:
http://bee.mif.pg.gda.pl/ciasteczko...Gruppen/Lab_Gruppen_fP6400_Service_Manual.pdf
An, evidently, fully personal remark intended for new readers:
Such amplifiers are conceived for professional use. That means, with a business budget to buy the gear and a business budget to maintain the gear. Repair of such units is very difficult and normally requires a specialist. This is why you need a business budget.
You can buy them, in particular second hand, for money you can pay and the specs are impressive. If you need that kind of power privately, I will let you decide on. But, as the repair is only for very skilled and experienced persons, don't forget a budget for maintenance.
I previously compared it to a Lamborghini engine. If you are used to do trivial maintenance on your VW Golf, will you also get away with maintaining a 12 cylinder Lamborghini?
Look at the many fine photos Chris found and get an idea.
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Labgruppen FP is somewhat of a myth.
Interesting circuits, though (thanks for service manual). I don't know if is this is the problem, but has someone noticed C6,C13 in A20TDL board? As these electrolytics dry with age the amplifier loses its power capability.
If it is not an amplifier board or regulator board problem, signal limiters are at IN2GTD board. A SMPS problem is easily discarded by measuring the rails while recreating fault scenario.
Interesting circuits, though (thanks for service manual). I don't know if is this is the problem, but has someone noticed C6,C13 in A20TDL board? As these electrolytics dry with age the amplifier loses its power capability.
If it is not an amplifier board or regulator board problem, signal limiters are at IN2GTD board. A SMPS problem is easily discarded by measuring the rails while recreating fault scenario.
Starting point: "...it still works, sounds fine, and makes no noise, just lower output, and will then run like that all day."
My logic then tells me that if it affects both channels in the same way, it is not an amplifier circuit defect because then the channels would be affected individually and differently. If, it is a power supply circuit issue, it would not cause a controlled (distortion-free) reduction of the volume that remains stable. A power supply circuit failure would tend to cause distortion as the supply voltage drops, probably unsymmetrically, and would have no direct influence on the gain.
For me to see, it is most likely an intentional reduction of the signal level/gain that is invoked unintentionally. Therefore, I imagine it relates to a control circuit (protection) issue.
Had it been possible to get access to the circuits without dis-assembly, I would go backwards from the output with my oscilloscope and see how far back the signal amplitude would drop when the "small pop" appears. Then, I would know where the amplifier circuit was stimulated to reduce amplitude. From there, I could figure out which circuit stimulated the amplifier circuits. And then why that stimulation signal was generated.
With this mechanical construction it may be difficult to get access.
The professional approach is probably: Which module is likely to be the culprit? -> replace that module -> works? -> yes, debit the business maintenance account with that much.
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Hi
i just google your amp.....heavy mechanical construction and compress build.
Maybe its a nice try to start with seperate the left channel from R channel testing.
e.g. disconnect the left channel as good as possible completely. is the strange pop still there? then try the R-Channel.
...so please be aware of the hazardous psu part --> there is more voltage as you might think !-if there is a SMPS...--up to 400V
discharging a cap with 1 HAND is recommended !!!
chris
That's a great idea.
- And yes, I know my way around electronics extremely well. (including old tube amps.)
Thanks!
I don't know if i would recommend these amps. I have 3 of them costing me a total of £3000 used price.
Perhaps i am just the most unlucky person on earth but two of them self destructed.
Basically the transformer is very badly made. (If you have the old square shaped high voltage transformer and not the round style one.)
It is made perhaps from ferrite and at least one of the ends is glued on. The glue becomes old and the end of the transformer becomes loose. This caused a voltage spike which blows several capacitors and i am yet to find out what else is blown. The first one was shooting sparks out of the front as the caps blew, it also tripped the main building. The 2nd one blew an internal fuse and some caps but not sure what else yet. It's quite a mission to remove the transformer. My plan is to try to glue it back together, replace the caps and hope for the best or i'm £2k down right now.
Regarding your issue, if it wasn't for the pop sound i would have suggested looking at the dip switches at the rear. The dip switches allow you to change many settings such as bridged mode and a whole amount of different gain settings. I have seen faulty dip switches on disco lights where they become very unreliable.
If it's a capacitor you might be able to see if it's gone bad by looking for bulged tope or a split in the heatshrink coating.
Did you ever find the issue?
The first time one of these blew on me i put it down to wheeling the amp rack over bums in the cold and told lab that it's not much of a touring amp.
The 2nd time which was just now, the amp was switched on but fully muted at the dsp, so basically it was just sitting there as i have around 10K setup in my house for lockdown. In the evenings i often mute the bass (if my son is sleeping) and watch youtube on the system. The Amp rack has been in my home for over a year and it sees a few hours of use per day but only in the last 6 months.
At new years i had it running flat out for a short while and have used the amp on a few occasions since, but this evening it was just sitting there muted, but switched on and then i smelt that awful capacitor smell. I was going around my house trying to find out what was burning out and then i noticed the power lamps were off, i immediately removed the casing and found 2x blown caps on the 2nd stage of the PSU.
Then i checked the transformer and it had indeed become unglued.
I'm currently trying to find someone else who has made the repair to see if i can pick up any tips. Lab wanted £600+ to repair each one and they won't sell me the transformer!
Perhaps i am just the most unlucky person on earth but two of them self destructed.
Basically the transformer is very badly made. (If you have the old square shaped high voltage transformer and not the round style one.)
It is made perhaps from ferrite and at least one of the ends is glued on. The glue becomes old and the end of the transformer becomes loose. This caused a voltage spike which blows several capacitors and i am yet to find out what else is blown. The first one was shooting sparks out of the front as the caps blew, it also tripped the main building. The 2nd one blew an internal fuse and some caps but not sure what else yet. It's quite a mission to remove the transformer. My plan is to try to glue it back together, replace the caps and hope for the best or i'm £2k down right now.
Regarding your issue, if it wasn't for the pop sound i would have suggested looking at the dip switches at the rear. The dip switches allow you to change many settings such as bridged mode and a whole amount of different gain settings. I have seen faulty dip switches on disco lights where they become very unreliable.
If it's a capacitor you might be able to see if it's gone bad by looking for bulged tope or a split in the heatshrink coating.
Did you ever find the issue?
The first time one of these blew on me i put it down to wheeling the amp rack over bums in the cold and told lab that it's not much of a touring amp.
The 2nd time which was just now, the amp was switched on but fully muted at the dsp, so basically it was just sitting there as i have around 10K setup in my house for lockdown. In the evenings i often mute the bass (if my son is sleeping) and watch youtube on the system. The Amp rack has been in my home for over a year and it sees a few hours of use per day but only in the last 6 months.
At new years i had it running flat out for a short while and have used the amp on a few occasions since, but this evening it was just sitting there muted, but switched on and then i smelt that awful capacitor smell. I was going around my house trying to find out what was burning out and then i noticed the power lamps were off, i immediately removed the casing and found 2x blown caps on the 2nd stage of the PSU.
Then i checked the transformer and it had indeed become unglued.
I'm currently trying to find someone else who has made the repair to see if i can pick up any tips. Lab wanted £600+ to repair each one and they won't sell me the transformer!
I can recommend you to get in touch with Stefan Kosmalla.
He has an amplifier repair shop in germany and is very focused on PA amplifier repairs. Especially also on those FP series.
I guess that he can help you.
Rockline Sound & Light, Veranstaltungtechnik und Reparatur - Impressum
He has an amplifier repair shop in germany and is very focused on PA amplifier repairs. Especially also on those FP series.
I guess that he can help you.
Rockline Sound & Light, Veranstaltungtechnik und Reparatur - Impressum
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