Hi Folks:
I just bought an 845-3 with the 300b cathode follower. I am now calmly awaiting its arrival and contemplating modifications. I agree that using a 300b as a follower is a little weird. I plan on modding the thing after a whiile. I was thinking of using a Lundahl interstage in the plate of the 300B. I'd have to drop the voltage going to it somehow as it looks to be fairly high in the Mr.Liang circuit. Any advice or comments would be welcome.
Thanks -- Minto
I just bought an 845-3 with the 300b cathode follower. I am now calmly awaiting its arrival and contemplating modifications. I agree that using a 300b as a follower is a little weird. I plan on modding the thing after a whiile. I was thinking of using a Lundahl interstage in the plate of the 300B. I'd have to drop the voltage going to it somehow as it looks to be fairly high in the Mr.Liang circuit. Any advice or comments would be welcome.
Thanks -- Minto
Good luck with your Mr L....
If you have been following my posts you'll be aware I'm starting mine from scratch. After looking at various mods, I decided to build it more or less as is but using upgraded (better?) components. I did mod the Bias circuit for the 845's. And I also did away with the delay circuits. Instead I am using thermionic diodes in the HT paths of the 300's and the 845's. I think buying the unit and modifying it is the way to go as far as price goes. As parts alone have cost me just about $3000.
Also there are a few design headaches with trying to stuff it all in one box of reasonable size.
Can't help with the mods you propose in the anode circuit of the 300 but I'm sure others will.
JB
If you have been following my posts you'll be aware I'm starting mine from scratch. After looking at various mods, I decided to build it more or less as is but using upgraded (better?) components. I did mod the Bias circuit for the 845's. And I also did away with the delay circuits. Instead I am using thermionic diodes in the HT paths of the 300's and the 845's. I think buying the unit and modifying it is the way to go as far as price goes. As parts alone have cost me just about $3000.
Also there are a few design headaches with trying to stuff it all in one box of reasonable size.
Can't help with the mods you propose in the anode circuit of the 300 but I'm sure others will.
JB
Hi John:
I wish there was some more real estate on the Mr. Liang for tube rectification but at 100lbs bigger may not be so good. I hope you are building monoblocks otherwise it'll weigh a ton. I think you're smart to design a tube power supply. I've always like the way it sounded.
I'd like to see your circuit. Photos of the build would be great too. I have built a lot of push pull amps but never anything with really high voltage so I am very curious.
My Audioromy 845 is the first SE amp I have owned. The Audioromy has inspired me to buy the Mr. Liang. I have heard quite a few 300B and 2A3 amps but the 845 is in a different world. I hear that the copper plate GM70 is even better. Have you considered playing around with that tube?
Thanks all the best in your project. Please keep me posted.
Ciao and be well -- Minto
I wish there was some more real estate on the Mr. Liang for tube rectification but at 100lbs bigger may not be so good. I hope you are building monoblocks otherwise it'll weigh a ton. I think you're smart to design a tube power supply. I've always like the way it sounded.
I'd like to see your circuit. Photos of the build would be great too. I have built a lot of push pull amps but never anything with really high voltage so I am very curious.
My Audioromy 845 is the first SE amp I have owned. The Audioromy has inspired me to buy the Mr. Liang. I have heard quite a few 300B and 2A3 amps but the 845 is in a different world. I hear that the copper plate GM70 is even better. Have you considered playing around with that tube?
Thanks all the best in your project. Please keep me posted.
Ciao and be well -- Minto
Mr Liang 845-3
Here is an update on my Mr L build with some pictures for those interested. (if I can figure how to attach them!).
All transformers have been fitted to the chassis. The 800Volt job is topside in its own metal box (vented top and bottom). the OPT's are also topside as one might expect. the large choke is between the two OPTs. The bias air-core transformer is inside and to one side, it is fitted to the curve of the chassis side. The small choke is on the other side.
The remaining 400V transformer, which has most of the heater winding is also mounted underneath in the centre. Valve sockets are installed.
Note two middle front are the power diodes, which I have used to replace the timing circuits.
Cherry-wood faceplate (what a job, I'm no carpenter that's for sure!) is cut and ready for final sanding, stain and varnish.
Next job is to get the heating circuits wired, then figure where to put all the big capacitors. I have some nice circuit boards, to mount the rest of the components on.
For those of you in the know I'm calling my amp Pan Slitek.
Your most valuable comments appreciated as always.
John
Photo's are too big to attach so it seems...I'll get back to you
Here is an update on my Mr L build with some pictures for those interested. (if I can figure how to attach them!).
All transformers have been fitted to the chassis. The 800Volt job is topside in its own metal box (vented top and bottom). the OPT's are also topside as one might expect. the large choke is between the two OPTs. The bias air-core transformer is inside and to one side, it is fitted to the curve of the chassis side. The small choke is on the other side.
The remaining 400V transformer, which has most of the heater winding is also mounted underneath in the centre. Valve sockets are installed.
Note two middle front are the power diodes, which I have used to replace the timing circuits.
Cherry-wood faceplate (what a job, I'm no carpenter that's for sure!) is cut and ready for final sanding, stain and varnish.
Next job is to get the heating circuits wired, then figure where to put all the big capacitors. I have some nice circuit boards, to mount the rest of the components on.
For those of you in the know I'm calling my amp Pan Slitek.
Your most valuable comments appreciated as always.
John
Photo's are too big to attach so it seems...I'll get back to you
Can't post photos
Sorry can't post pics.... file is too big.
If interested I could put then up on Kodak Gallery, but I'd need your e-mail address.?? Unless you have an another idea ?
j
Sorry can't post pics.... file is too big.
If interested I could put then up on Kodak Gallery, but I'd need your e-mail address.?? Unless you have an another idea ?
j
There are several sites that specialize in hosting pictures that don't require viewers to have a membership: imageshack being one very commonly used here..
Link here: www.imageshack.us/
Download and install the open source image editing software GIMP which is available for windows. This will allow you to easily crop and/or compress your image files so that some may be posted here as well as on imageshack or elsewhere.
Link here: www.gimp.org/windows/
Link here: www.imageshack.us/
Download and install the open source image editing software GIMP which is available for windows. This will allow you to easily crop and/or compress your image files so that some may be posted here as well as on imageshack or elsewhere.
Link here: www.gimp.org/windows/
Mr Liang 845-3 - photos
Thanks Kevin, Photos are now on
Link here: www.imageshack.us/
look for "panslitek845"
John
Thanks Kevin, Photos are now on
Link here: www.imageshack.us/
look for "panslitek845"
John
Hi John,
That search didn't return anything unfortunately. Try creating a link directly to the picture and post it here.
Kevin
That search didn't return anything unfortunately. Try creating a link directly to the picture and post it here.
Kevin
Mr Liang
Hi
I just wondered if anyone has had a go at changing the opt on Mr Liang 845 amplifier.I seem to remember that someone on this forum was contemplating doing this
regards
Hi
I just wondered if anyone has had a go at changing the opt on Mr Liang 845 amplifier.I seem to remember that someone on this forum was contemplating doing this
regards
Mr Liang OPT
Hi David et al,
Yes I think I was the one you are referring to.
I had MkI in for repair and the OPT was u/s. The customer didn't want the expense so I bought it and fitted a pair of Sowter OPTxs 5K/8R type SE09.
I found that hum pickup from the power txs a problem until I rotated both the OPTxs for minimum hum. I also fitted humbucking to the 845s and DC heaters to the front end valves. I also got rid of the volume control and drive it from a very low impedance preamp output
I am at present repairing/modding another 845/3 similarly, but this one had a s/c turns smoothing choke replaced with a Hammond unit.
I am now at the stage of doing the humbucking and DC heater mods. Interestingly this one was supplied with metal 6AC7s for the front end and as far as I can see from the data this is a much better match to the 6J4P, however it is essential the pin 1 on this valve is earthed for safety and screening purposes. I also found that on the /3 version the PCB is automatically earthed through the metal mounting pillars so I changed these for nylon types and did the standard earth stand off of 10R in parallel with 0.1µF.
Engineering point. The chassis is Stainless steel, this is a bit of a so and so to work on. To drill it you will need Cobalt based drills and some cutting oil for clean holes. RS sell some good ones.
Hope these details will help people to convert a good cheap basic amp into a very good amp.
John Caswell
Hi David et al,
Yes I think I was the one you are referring to.
I had MkI in for repair and the OPT was u/s. The customer didn't want the expense so I bought it and fitted a pair of Sowter OPTxs 5K/8R type SE09.
I found that hum pickup from the power txs a problem until I rotated both the OPTxs for minimum hum. I also fitted humbucking to the 845s and DC heaters to the front end valves. I also got rid of the volume control and drive it from a very low impedance preamp output
I am at present repairing/modding another 845/3 similarly, but this one had a s/c turns smoothing choke replaced with a Hammond unit.
I am now at the stage of doing the humbucking and DC heater mods. Interestingly this one was supplied with metal 6AC7s for the front end and as far as I can see from the data this is a much better match to the 6J4P, however it is essential the pin 1 on this valve is earthed for safety and screening purposes. I also found that on the /3 version the PCB is automatically earthed through the metal mounting pillars so I changed these for nylon types and did the standard earth stand off of 10R in parallel with 0.1µF.
Engineering point. The chassis is Stainless steel, this is a bit of a so and so to work on. To drill it you will need Cobalt based drills and some cutting oil for clean holes. RS sell some good ones.
Hope these details will help people to convert a good cheap basic amp into a very good amp.
John Caswell
Mr Liang Heaters for 845s
Hi all,
Sorry forgot to mention this minor problem I found on a recent Mr Liang 845/2/3.
The 845 heaters were out, this was traced to the 4 pin Amp/Molex plug/socket on the PSU board being overheated due to excessive current flow through it ie 10V x 3A x 2 = 60 VA. It had cooked. On my Mr Liang the heaters for the 845s are hard soldered to the underside of the PSU PCB so I did the same to the 845/2/3 and all was well. I feel this is a worthwhile mod and it gets rid of a potential trouble spot.
If you are not sure what you are doing leave well alone!
John Caswell
Hi all,
Sorry forgot to mention this minor problem I found on a recent Mr Liang 845/2/3.
The 845 heaters were out, this was traced to the 4 pin Amp/Molex plug/socket on the PSU board being overheated due to excessive current flow through it ie 10V x 3A x 2 = 60 VA. It had cooked. On my Mr Liang the heaters for the 845s are hard soldered to the underside of the PSU PCB so I did the same to the 845/2/3 and all was well. I feel this is a worthwhile mod and it gets rid of a potential trouble spot.
If you are not sure what you are doing leave well alone!
John Caswell
845-3 re the front end 6J4P....
As previously posted I am building my own 845-3 from scratch.
I have the Russian version of the 6J4P (Cyrillic characters).
However the pin-outs appear to be different......
Pin........Russian..................English(per 845-3 schematic)
1.......grid....................internal screen ? (ground/chassis)
2.......suppressor*......Not shown ( heater?)
3.......heater................suppressor
4.......heater................grid
5.......anode................cathode
6.......screen................screen
7.......cathode..............Not shown (heater?)
8........N/A.................... anode
* Pin 2 shows internal connection to an internal screen on the Russian tube.
Is this just a misprint on the 845-3 schematic.... if not,
obviously, one would be in big trouble if you thought they were a direct socket to socket replacement.... anyone care to comment?
As previously posted I am building my own 845-3 from scratch.
I have the Russian version of the 6J4P (Cyrillic characters).
However the pin-outs appear to be different......
Pin........Russian..................English(per 845-3 schematic)
1.......grid....................internal screen ? (ground/chassis)
2.......suppressor*......Not shown ( heater?)
3.......heater................suppressor
4.......heater................grid
5.......anode................cathode
6.......screen................screen
7.......cathode..............Not shown (heater?)
8........N/A.................... anode
* Pin 2 shows internal connection to an internal screen on the Russian tube.
Is this just a misprint on the 845-3 schematic.... if not,
obviously, one would be in big trouble if you thought they were a direct socket to socket replacement.... anyone care to comment?
Mr'Liang 845 and metal 845 version
Has anyone tested the Shuguang 845c (metal version of 845) in the MR Liang LS-845? Does really not work on this amp?
Has anyone tested the Shuguang 845c (metal version of 845) in the MR Liang LS-845? Does really not work on this amp?
Got a Mr. Liang 845 used and abused need advice on how to troubleshoot
Greetings,
Just bought an LS845 ( I think it's a mkIII) with an unstable bias (meter pegs) but also comes with a lot of stuff not disclosed, such as:
0. no tube cage
1. misaligned mounting of "upgraded" 300B tube socket
2. completely toast 0.22uF film cap on 1 channel
3. bad bias meter LED
4. many screws missing
5. top plate installed upside down smack on top of mismatching screws ( completely marred the plate)
The owner claims to have observed the bias meter peg problem when he upgraded the tube sockets and silver wiring (ha! silver wiring from grid bias resistors to 845 ???)
In short it's in pretty miserable shape and non-operational condition but I'm up for the challenge to revive this puppy.
Well anyway, initially I measured across the 36k resistor in series with the bias trim pot before the wire leads to 845 grid and found it to be only 20k and after resoldering it it seems to get back to 36k.
After replacing the bad 0.22uF cap (thats the other channel, neither channel was working when I 1st got it!) Everything worked for about 15 minutes but when I powered it on a 2nd time time the bias on the R channel pegged again.
Wondering if any fellow DIYaudio-ers have encountered this problem and what might be a quick diag / fix.
If no suggestions I will probably replace the 10k 36k resistors around the biasing trim pot and connect that piece of to the 845 board directly to the 36k resistor to eliminate any possibility of flakey resistors / shorts on the PCB.
Another step I am contemplating is to disconnect that lead of the grid that connects to the 0.47uF coupling cap.
Thanks!
Greetings,
Just bought an LS845 ( I think it's a mkIII) with an unstable bias (meter pegs) but also comes with a lot of stuff not disclosed, such as:
0. no tube cage
1. misaligned mounting of "upgraded" 300B tube socket
2. completely toast 0.22uF film cap on 1 channel
3. bad bias meter LED
4. many screws missing
5. top plate installed upside down smack on top of mismatching screws ( completely marred the plate)
The owner claims to have observed the bias meter peg problem when he upgraded the tube sockets and silver wiring (ha! silver wiring from grid bias resistors to 845 ???)
In short it's in pretty miserable shape and non-operational condition but I'm up for the challenge to revive this puppy.
Well anyway, initially I measured across the 36k resistor in series with the bias trim pot before the wire leads to 845 grid and found it to be only 20k and after resoldering it it seems to get back to 36k.
After replacing the bad 0.22uF cap (thats the other channel, neither channel was working when I 1st got it!) Everything worked for about 15 minutes but when I powered it on a 2nd time time the bias on the R channel pegged again.
Wondering if any fellow DIYaudio-ers have encountered this problem and what might be a quick diag / fix.
If no suggestions I will probably replace the 10k 36k resistors around the biasing trim pot and connect that piece of to the 845 board directly to the 36k resistor to eliminate any possibility of flakey resistors / shorts on the PCB.
Another step I am contemplating is to disconnect that lead of the grid that connects to the 0.47uF coupling cap.
Thanks!
My Liang 845 is fixed....
took a lot of effort to undo the "teflon tube socket" mess up and the "silver wiring" debacle and the coupling cap barbeque + hazardous solder burnt to the naked strands wires + a bad cathode resistor (the only thing not fixed is a blown LED in the bias meter)
The seller really tried hard to break this amp!
System powers up plays music but clips the way low powered set soft clips at moderate levels.
Well I am playing through AValon Eidolons and Quad 989s and dont have 92db+ speakers to test.
Can anyone confirm that this amp (845-3, 300B option, graphite plate 845)
can actually drive real world speakrs of say 88dB/W/m?
Also the sound is not refined at all, not squeaky or glassy but has a coarse grainy texture to it.
Anyone tried swapping out all the diodes to hexfreds and schottky and replacing the
Kung Pao Chicken Licon brand lytics w Nichicon?
Thanks.
took a lot of effort to undo the "teflon tube socket" mess up and the "silver wiring" debacle and the coupling cap barbeque + hazardous solder burnt to the naked strands wires + a bad cathode resistor (the only thing not fixed is a blown LED in the bias meter)
The seller really tried hard to break this amp!
System powers up plays music but clips the way low powered set soft clips at moderate levels.
Well I am playing through AValon Eidolons and Quad 989s and dont have 92db+ speakers to test.
Can anyone confirm that this amp (845-3, 300B option, graphite plate 845)
can actually drive real world speakrs of say 88dB/W/m?
Also the sound is not refined at all, not squeaky or glassy but has a coarse grainy texture to it.
Anyone tried swapping out all the diodes to hexfreds and schottky and replacing the
Kung Pao Chicken Licon brand lytics w Nichicon?
Thanks.
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