the black goop is supposed to be there. I'm not sure why -- maybe for mechanical support of the transistors that it is on. It's also under the power transformer. If it's the same kind of goop that I have seen, it is hard and chips away instead of being flexible like silicone.
The boards look ok -- no burn marks. If there isn't any dc offset at the output (more than say 20 - 100 mV), it is probably ok.
The boards look ok -- no burn marks. If there isn't any dc offset at the output (more than say 20 - 100 mV), it is probably ok.
The black goop is there to support the transistors which because of their construction are easily damaged by vibration and mishandling. That series of transistors is no longer availible and tough to locate or substitute so definitely be careful and to not remove the goop or when servicing the amp!
Mike
Quatre QC500 schematic
Hello PH104,
I may be a fool trying to repair this GC-500 i just bought after reading all the horror stories about reliability. I've got one channel dead and one working. The bad board had bad predrivers, drivers, and 2 of the 6 outputs. All tantalums are toast. One had the side blown off. It looks like Quatre did some mods to a 250 model into a 500. The transformer is bigger, so they cut a half inch by 3 inch piece of the PCB to make clearance. Also looks like they used a 250 heat sink and drilled another set of holes for the extra pair of outputs. This one has been modified where they cut the trace,and soldered on a jumper wire to a new location. Hopefully this will improve reliability. I did read from this formum where user dot.system said that a 50ufd poly cap across the +60 to -60 greatly improves the reliability. Just no room to mount them. Well enough rambling. I was looking for possible source of a schematic, or any repair notes such as the emitter resistor voltage, and the potentiometer adjustment for DC Gain Cell. There is another pot labeled AC Gain Cell but it looks like it is turned all the way off. Any advice is greatly appreciated. It was good reading your replies to these posts.
thx
paul
Hello PH104,
I may be a fool trying to repair this GC-500 i just bought after reading all the horror stories about reliability. I've got one channel dead and one working. The bad board had bad predrivers, drivers, and 2 of the 6 outputs. All tantalums are toast. One had the side blown off. It looks like Quatre did some mods to a 250 model into a 500. The transformer is bigger, so they cut a half inch by 3 inch piece of the PCB to make clearance. Also looks like they used a 250 heat sink and drilled another set of holes for the extra pair of outputs. This one has been modified where they cut the trace,and soldered on a jumper wire to a new location. Hopefully this will improve reliability. I did read from this formum where user dot.system said that a 50ufd poly cap across the +60 to -60 greatly improves the reliability. Just no room to mount them. Well enough rambling. I was looking for possible source of a schematic, or any repair notes such as the emitter resistor voltage, and the potentiometer adjustment for DC Gain Cell. There is another pot labeled AC Gain Cell but it looks like it is turned all the way off. Any advice is greatly appreciated. It was good reading your replies to these posts.
thx
paul
Jam, great to hear from another quatre owner. which ones did you have ? GC500 ? was curious if you ever tried to help with the stability by adding some mods? another quatre owner said he had good luck by adding a 50ufd poly cap between the +60 and -60 on the circuit board near the outputs. If i do dump the guts, what other amp would you recommend ? Leach ? thanks muchA suggestion.........gut the amp and replace with a different circuit. I have owned four of them and they all blew up and are a royal pain to repair, even if you can obtain the parts. I don't think they sound that good today considering the competition.
Jam
paul
i havethe dlh100 and its in working condition
i have the dlh 100 and its in working condition
Just found this thread. I rescued three Quatre amplifiers from the dumpster when I went by a local dealer who wanted them dead! One original Quatre DG250 (I'm at work, they are home so I may have to correct that number). It is the one with the cover that has no sides and uses RCA410 transistors. It had -60 volts one the left channel after about 10 minutes of operation. One of the MPS-u60 transistors was intermittant so, once replaced, it works but has a tremendous turn on thump. I just turn that one on then connect the speaker leads. The second was a QC250C. It worked fine for about a month and blew one output. It has 5 amp fuses on the circuit boards and one of them blew. It uses MJ15003 for outputs. I replaced the output and it is running again. The last is a QC500. It worked from the start and is still working. The 500 has mj15003 outputs but has an added pair. I love the sound of the original DG500. It has no fuses except a line fuse. I remember years ago these used to blast speakers to oblivion when they failed. I opened one up years ago and it looked like someone had spray painted everything brown it burned up so badly.
Now, my question. Did anyone ever get schematics on these critters. The early one has only two potentiometers. The appear to be bias and dc offset. The later ones have three potentiometers.
It seems to me the lack of vent holes in the cases was intentional. It kept the fire contained on the original DG250.
I worked at a dealer years(!) ago and the biggest complaint on the later generations was chassis hum. Maybe that is the reason for the black goop under the power transformer. We found B&W DM6 loudspeakeers could set one of these amps off on turn on, sometimes damaging the speaker. They all loved Magneplanars, especially any Tympani version.
All in all, I like them. And, like I asked, any schematics?
Now, my question. Did anyone ever get schematics on these critters. The early one has only two potentiometers. The appear to be bias and dc offset. The later ones have three potentiometers.
It seems to me the lack of vent holes in the cases was intentional. It kept the fire contained on the original DG250.
I worked at a dealer years(!) ago and the biggest complaint on the later generations was chassis hum. Maybe that is the reason for the black goop under the power transformer. We found B&W DM6 loudspeakeers could set one of these amps off on turn on, sometimes damaging the speaker. They all loved Magneplanars, especially any Tympani version.
All in all, I like them. And, like I asked, any schematics?
I used to own the GC-500, which was plagued with parasitic oscillation. Years ago, a friend of mine at Purdue Audio in North Jersey put the beast on their bench...his singular comment was..."This amp was built on the ragged edge of instability." The amp subsequently blew the outputs and had to be returned to Bootjer 3 times....at the time, Bootjer was building these out of his garage in Reseda, California.
After the third time, Bootjer stopped answering the phone. And I was using these amp on Magnepans MG IIAs at the time. This amp was a total loss and the company folded quickly thereafter. Very sad. A substantial financial loss for a young audiophile at the time.
After the third time, Bootjer stopped answering the phone. And I was using these amp on Magnepans MG IIAs at the time. This amp was a total loss and the company folded quickly thereafter. Very sad. A substantial financial loss for a young audiophile at the time.
I just finished repairing a GC500 (late production). I actually was curious as to the failure of the MPSU60/10 devices as when I got the first channel running I had the 2SA968/C2238 devices in the four known problem spots. I am getting with the VI limiting disconnected, 260 watts a channel/8 ohms. I am not going to beat a set of MJ15003/4 devices to death into a four ohm load to see what happens. Just not enough output SOA in my opinion.
I did get curious as to the deaths of the VAS devices and installed four good ones to see if they would die at clipping. They clip just as well as the replacements but I noticed that they ran much hotter than the heatsinks. A bit of investigation showed the little aluminum heat sinks are not tight enough to allow the heat to escape. I drilled and screwed the sinks to the devices and they actually run cooler than the replacements. I now have all the original type devices in the amplifier and will see how they are now that they run cooler. I use my other 500 on Magneplanar IV loudspeakers and I play it at fairly loud volumes once and awhile. It has no VI limiting either.
I'm going to put this one in everyday use for know to check reliability.
I would like to add two additional outputs per side but unlike the 250 version, the heatsink has no additional room.
I did get curious as to the deaths of the VAS devices and installed four good ones to see if they would die at clipping. They clip just as well as the replacements but I noticed that they ran much hotter than the heatsinks. A bit of investigation showed the little aluminum heat sinks are not tight enough to allow the heat to escape. I drilled and screwed the sinks to the devices and they actually run cooler than the replacements. I now have all the original type devices in the amplifier and will see how they are now that they run cooler. I use my other 500 on Magneplanar IV loudspeakers and I play it at fairly loud volumes once and awhile. It has no VI limiting either.
I'm going to put this one in everyday use for know to check reliability.
I would like to add two additional outputs per side but unlike the 250 version, the heatsink has no additional room.
Hello, all!
Is there any hope of finding schematics for the DG250 series? I have owned from new 1@ DG250-C and DG250. They have never given any problems (DG250 C) always driving Magnepan Typani III bass panels in a tri-amped system, the DG250 driving Altec VOT A7-500 speakers in another system.
Now I think it prudent to pull them both down to rebuild before some ¨issue¨ takes then down.
Any hope to get the schematics?
Thank you.
Is there any hope of finding schematics for the DG250 series? I have owned from new 1@ DG250-C and DG250. They have never given any problems (DG250 C) always driving Magnepan Typani III bass panels in a tri-amped system, the DG250 driving Altec VOT A7-500 speakers in another system.
Now I think it prudent to pull them both down to rebuild before some ¨issue¨ takes then down.
Any hope to get the schematics?
Thank you.
I have the schematic for the DG250. I will scan it and post it next week. I got my Quatre amps (2) DG250, (1) GC250C and (2) GC500 amps and found out that the majority of the problems were caused by the small aluminum heatsinks on the VAS transistors. Over time, they relax and don't make contact with the tab on the transistor. I carefully drilled them and used screws to attach them.On one of the DG250 amps, it oscillated and the protect devices overheated. Check all of the resistors in the protect stage. One resistor was about 250 ohms too high. On one dg250 (a really tortured one) I pulled the protect loose and it puts out around 180 watts per channel. I use mine to drive Tympani IV full range. Any of them can produce lease breaking volume. All but one GC500 have original outputs in them. I do use a "speaker saver" on my system but it the Quatre amps have been reliable once the heatsink fix was installed.
Hello!
Great to read your posting(s).
The Quatre amps do indeed have a unique sound - sound stage feel. Sort of like a cross between thick black velvet and thick soft wide wale corduroy ! Superb bass detail, and woodwinds are special too.
Anyway, Thank you.
I'll scan the schematic and post it. I have to say, I like the Quatre amps. My girl friend tortures a GC500 all Sunday morning. My Tympani 4 Magneplanars are not a easy drive. Like I mentioned earlier, the heatsinks on the VAS transistors are a very bad design. Once they loosen up they fail rapidly.