Cheap Chinese 6P3P kit
- Thread starter Big & Pink
- Start date
Kegger
R.I.P. 1/12/1966 - 6/1/2017
You need to build the whole amp, get tubes to draw current then you'll get actual voltages.
(schematic says 315vdc B+, but once built with a load)
You should end up with say 355-375vdc of B+ with that power transformer, which is fine for
the output tubes, just may have to adjust there cathode resistor, which we can do on here.
(schematic says 315vdc B+, but once built with a load)
You should end up with say 355-375vdc of B+ with that power transformer, which is fine for
the output tubes, just may have to adjust there cathode resistor, which we can do on here.
bobrown14
Super Member
Awesome, thanks for the explanation. I was wondering why the rectifier looked OK (glowing) but my voltage is what it is.
I'm still not hunky dorey with the power supply and the ground the way it is. Seems dangerous to me, with the negative rail attached to the chassis with no X2 cap/reistor. I got a little jolt from the chassis with the AC mains unplugged (caps still charged from like 3-4 hours ago from last power on, they were for sure charged.. any suggestions on keeping me alive. I have an very old house, the 120V mains pugs are 3 pronged but I can't ASSume they are for sure grounded. After all an "electrician" owned this house before me.
Oh yeah - IMPORTANT note here:
I tested the 330uF cap supplied with this kit and it measured 230uF - its the one that is labeled United Chem-icon. I replaced it with a tested new Nichicon GW. Just lettin ya's know... 230uF 330uF close enough?... not really. Probably mis-labeled (and I'm being nice). I just had a feeling ... so before I hooked it up I tested the cap and replaced it with a new one.
So I should be good to hook up my inputs and volume pot and plug the rest of the tubes in.
Can anyone share what voltages I should see at the preamp tube?
Cheers,
Bob
shelly_d
Not An Audiophool
Best way to make sure that power supply caps will discharge once you turn the amp off is to mount resistors directly across them. They will draw a bit more current from the power supply but will serve to drain the caps once the power is turned off. I would choose a value that would draw perhaps about 5 mA. That's more of a guess on my part then a real good design objective so if someone has a better objective or more real number then that please leap in here.
To find the value of the resistor take the power supply voltage of 430 volts and divide it by the current you pick, in this case 5 mA or .005 Amps. So you need a resistor that is: 430 ÷ .005 = 86 KΏ. To find the power the resistor will dissipate square the current and then multiply by the value of the resistor. In this case, .005^2 * 86,000 = 2.15 watts. So you would need a resistor capable of dissipating twice that or a 5 watt resistor.
If you decided to drain at 1 mA or .001, you would need a 430KΏ resistor (430÷.001=430,000). The power dissipated would be .001^2*430000=.43 watts requiring a 1 watt resistor.
Hope this is helpful.
Shelly_D
bobrown14
Super Member
Very helpful indeed. Thanks for the info. Now where would be the best place to install the bleeder resistor(s)? I could just solder a bleed resistor across both legs on the 47uF cap (C1) and/or across the legs of the 330V cap (C2).
If I install the bleeder across C1, it should bleed off the rest of the caps in the circuit correct?
I found a 330K 2watt CF2 Stackpole resistor in my parts bin. Good to 500V working voltage.
Cheers,
Bob
bobrown14
Super Member
It works!!
Yess-in-deed, this amp works and I have sound. Plugged in a tuner direct to inputs and a set of cheep workbench speakers, and dang, it makes sound. I'll post some pics here later once I turn it over and take voltage measurements to see if we need to tweek it a little. My first point to point tube amp in the books. I got a little scare there for a minute when the tubes warmed up the first few seconds there was a slight whistle snap crackle but it went away. Pretty quiet, don't hear any hum at all but my bench speakers are what they are (left over center channels from HT system), good'nuf for testing.
Thanks all for the help so far. As always AK rocks.
Cheers,
Bob
Yess-in-deed, this amp works and I have sound. Plugged in a tuner direct to inputs and a set of cheep workbench speakers, and dang, it makes sound. I'll post some pics here later once I turn it over and take voltage measurements to see if we need to tweek it a little. My first point to point tube amp in the books. I got a little scare there for a minute when the tubes warmed up the first few seconds there was a slight whistle snap crackle but it went away. Pretty quiet, don't hear any hum at all but my bench speakers are what they are (left over center channels from HT system), good'nuf for testing.
Thanks all for the help so far. As always AK rocks.
Cheers,
Bob
MickeySmile
Well-Known Member
Yess-in-deed, this amp works and I have sound. Plugged in a tuner direct to inputs and a set of cheep workbench speakers, and dang, it makes sound. I'll post some pics here later once I turn it over and take voltage measurements to see if we need to tweek it a little. My first point to point tube amp in the books. I got a little scare there for a minute when the tubes warmed up the first few seconds there was a slight whistle snap crackle but it went away. Pretty quiet, don't hear any hum at all but my bench speakers are what they are (left over center channels from HT system), good'nuf for testing.
Thanks all for the help so far. As always AK rocks.
Cheers,
Bob
Could you put some photos under its skirt. BTW what the fuse rate for it?
Thanks!
Binh
shelly_d
Not An Audiophool
Just saw this question. Sorry, busy with Passover and such. I just went back and looked at the schematic and if the one I looked at is the one you are wiring to (the one with Kegger's suggestion for single tube operation) then there are 2 equally good places for a bleeder resistor. That would be across either of the first two caps out of the rectifier. Placing it across the 2nd of them will allow the resistor in between the two to drop the voltage the bleeder will see by just a bit and therefore reduce the power it will dissipate which would be helpful but on the other hand across the 2nd of them will drain the cap that sees the highest voltage faster. Either way, it is a very minor decision, either will do the job.
Shelly_D
PS. That resistor should work fine. It will bleed at 1.3 mA initially and dissipate 1/2 watt.
Last edited:
bobrown14
Super Member
Thanks for the info, I put it across the 1st cap. the big 330uF cap has a lot of wires already there. When I initially did a sound check I had forgot to hook up the NFB resistors. The sound without NFB was not good, VERY muddy. After the NFB resistors I have decent sound. I swapped out the 6P3P tubes for some Sovtek 6L6WGT+ tubes due to some intermittent cutoff on one of the 6P3P tubes. I have this amp running some Dahlquist DQ-10 which are very inefficient. So the volume is low so when I turned up the volume on the preamp to like 1 o'clock and I think there's too much signal and overloaded the 6P3 tubes. I could see the plate cut out and turn back on. The Sovtek tubes work fine and actually sound pretty good. I know the DQ-10s are not a very good match with this amp but if they can drive them without complaint then I can safely try this amp on my horn loaded speakers. So I'm running them with the DQ-10s for a while for break in and testing as I have another tube amp with other speakers set up right beside this amp so I can A-B for sound comparison. Sounds pretty good.
Cheers,
Bob
bobrown14
Super Member
6P3P NOS Rectifier
I just plugged in a different rectifier tube. I picked up a Mazda 5Y3GB with same specs as the 5Z4 that comes with this amp on Keggers info supplied somewhere here on AK. WOW is all I gotta say, this amps sound stage really opened up. I've never heard this much improvement with changing a rectifier tube. For anyone with one of these you just can't swap in any old 5Y3 for a 5Z4, only the Mazda version has the slow start like the 5Z4 does. I have better sound all around. So I'm running Sovtek 6L6WGT+, Mazda 5Y3GB rectifier and an real Russian 6N1 right now and I'm completely stoked with the sound, and that's with the bad match for SE amp - DQ-10 speakers. Gain is up pretty high in my preamp, say 11 o'clock but I LOVE the sound. Totally different better all around. The 5Y3 Mazda makes that little 5Z4 look like a stunted junky. The 5Y3 is a 3rd or more larger, like a REAL rectifier tube. I'll get some more pics up. Those 6L6WGT tubes look really nice with a blue glo. This amp looks like a REAL tube amp now, not bad. I'm glad I had the patience to wait out the ship issues, which to Siliconray's goodness have been squared away.
Attached is a pic of the 5Y3GB rectifier, sounded so good I just bought another one from the same guy I bought the first one from. Ebay seller from Hong Kong. Looks like he might have a collection of them. While I was typing this I decided to check Ebay for some more just in case an all, and there was another from the same seller. Bingo...
Spinning some LP's.. Mmmmmighty fine.
I guess I'm getting hooked real bad on the SE sound. Like a brown trout on opening day.
Cheers to the Kegger, yeah you right!
Bob
I just plugged in a different rectifier tube. I picked up a Mazda 5Y3GB with same specs as the 5Z4 that comes with this amp on Keggers info supplied somewhere here on AK. WOW is all I gotta say, this amps sound stage really opened up. I've never heard this much improvement with changing a rectifier tube. For anyone with one of these you just can't swap in any old 5Y3 for a 5Z4, only the Mazda version has the slow start like the 5Z4 does. I have better sound all around. So I'm running Sovtek 6L6WGT+, Mazda 5Y3GB rectifier and an real Russian 6N1 right now and I'm completely stoked with the sound, and that's with the bad match for SE amp - DQ-10 speakers. Gain is up pretty high in my preamp, say 11 o'clock but I LOVE the sound. Totally different better all around. The 5Y3 Mazda makes that little 5Z4 look like a stunted junky. The 5Y3 is a 3rd or more larger, like a REAL rectifier tube. I'll get some more pics up. Those 6L6WGT tubes look really nice with a blue glo. This amp looks like a REAL tube amp now, not bad. I'm glad I had the patience to wait out the ship issues, which to Siliconray's goodness have been squared away.
Attached is a pic of the 5Y3GB rectifier, sounded so good I just bought another one from the same guy I bought the first one from. Ebay seller from Hong Kong. Looks like he might have a collection of them. While I was typing this I decided to check Ebay for some more just in case an all, and there was another from the same seller. Bingo...
Spinning some LP's.. Mmmmmighty fine.
I guess I'm getting hooked real bad on the SE sound. Like a brown trout on opening day. Cheers to the Kegger, yeah you right!
Bob
Attachments
bobrown14
Super Member
Smoking transformer! YIkes
I think I just blew the transformer in this amp. I swapped in a pair of 807 tubes with socket adapters. After about 5 minutes the 5Y3 had a fire inside the tube which I caught after about 10 seconds, powered off. Took out the 5y3 swapped in the 5Z4 and put the 6L6 tubes back in and the amp worked for about 30 seconds and the tranny started to smoke. Damit. Looks like I'm going to need a new transformer. Is there a good one for this setup from Edcor/ Angela that someone can recommend?? Looks like I will have a challenge with size of a new one but I would be grateful for any suggestions.
I tried the 807s before with the 5Z4 rectifier and didn't have any issues. The rectifier looked like it went into thermal runaway ... fire inside the tube..Maybe 807 tubes not a good match for the 5Y3. ?? What else may I have blown?
Cheers,
Bob
I think I just blew the transformer in this amp. I swapped in a pair of 807 tubes with socket adapters. After about 5 minutes the 5Y3 had a fire inside the tube which I caught after about 10 seconds, powered off. Took out the 5y3 swapped in the 5Z4 and put the 6L6 tubes back in and the amp worked for about 30 seconds and the tranny started to smoke. Damit. Looks like I'm going to need a new transformer. Is there a good one for this setup from Edcor/ Angela that someone can recommend?? Looks like I will have a challenge with size of a new one but I would be grateful for any suggestions.
I tried the 807s before with the 5Z4 rectifier and didn't have any issues. The rectifier looked like it went into thermal runaway ... fire inside the tube..Maybe 807 tubes not a good match for the 5Y3. ?? What else may I have blown?
Cheers,
Bob
shelly_d
Not An Audiophool
Took a look at the Antek site for you. Your issue is the 5 volt filament winding for the rectifier. You might be able to use the 6.3 winding with a power dropping resistor in series with the rectifier winding. If the total currents work out this might work:
http://www.antekinc.com/details.php?p=730
Not very expensive and pretty robust. I'm using an Antek in my Stereo 70 and it serves very well.
Good Luck
Shelly_D
bobrown14
Super Member
I'm not sure about that Antek although I like them as I use them in my pre-amp.
From the schematic I need the following for a new transformer
300-0-300v Hv tap
3.15-0-3.15v heater taps for the 6N1
6.3v heaters for 2 6L6
5.0v heater taps for 5Y3/5Z4
All I see for the transformers with the 3.15-0-3.15 they don't come with another 6.3v tap.
Any help. I think the weird thing with this amp is the 6N1 tube with requires that 3.15-0-3.15 tap for the heaters. One 3.15 to one heater the other 3.15 to the other heater and 0(zero) to ground.
Also I need to figure out what caused the short and no blown fuse?? That's a tad troubling. Doesn't really give me a warm and fuzzy feeling, if ya dig me.
I pulled all the tubes and powered the amp back on and still getting smoke from the tranny. Probably toasted and winding are shorted inside. Shouldn't that cause the fuse to let go?
Cheers,
Bob
From the schematic I need the following for a new transformer
300-0-300v Hv tap
3.15-0-3.15v heater taps for the 6N1
6.3v heaters for 2 6L6
5.0v heater taps for 5Y3/5Z4
All I see for the transformers with the 3.15-0-3.15 they don't come with another 6.3v tap.
Any help. I think the weird thing with this amp is the 6N1 tube with requires that 3.15-0-3.15 tap for the heaters. One 3.15 to one heater the other 3.15 to the other heater and 0(zero) to ground.
Also I need to figure out what caused the short and no blown fuse?? That's a tad troubling. Doesn't really give me a warm and fuzzy feeling, if ya dig me.
I pulled all the tubes and powered the amp back on and still getting smoke from the tranny. Probably toasted and winding are shorted inside. Shouldn't that cause the fuse to let go?
Cheers,
Bob
See if siliconray can hook you up on a transformer? If the heater circuit shorted is may not be enough to blow the fuse?? Still a bit odd, I'll be if you let it run a meltdown would happen and the fuse should blow but it will not be pretty.I dont think a transformer can cost that much from siliconray, and the shipping could be air mail??
shelly_d
Not An Audiophool
You clearly need to replace the tranny. For the 6N1 thy way a 6.3 volt supply with a grounded center tap. That can be created artificially with a pair of resistors off one off the 2 6.3 volt taps of the transformer. Using a pair of 1% 1/4 watt resistors between 100 and 300 ohms will simulate the same thing. Tie each end of the 6.3 volt tap to one end of each resistor and the other end of each resistor goes to ground.
The transformer has 2 300 volt taps. Wire them in series and that connection to ground. That is your "center tap". The other two ends to your rectifier.
The only real issue is whether the 6.3 taps can supply enough current to supply all the tubes and run the rectifier tube, through a dropping resistor, to power the rectifier. Alternatively, using solid state diodes will eliminate the need for the 5 volt winding but increase the voltage on the plate of the tubes. Depending upon the limits of the tubes that may or may not be a bad thing.
Shelly_D
siliconray
Member
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