Checked voltages on cathode pin of el34 this is reading between 1 & 2.5 volts on each channel. I think I may have overheated the lm317's possibly. I suspected they may be part of the isdue so i have 5 more on order already. Annoying.
In your schematics in post #20 it says that B+ is 400 V. If true, than that is way too high.
In the "RH84 revision 2" B+ is 315 V.
In the "RH84 revision 2" B+ is 315 V.
Yes. This is part of my problem I dont know why. I built it to Mr kitics design 300-0-300 transformer, 47uf 1st cap, 10h 100mah choke, 200uf capacitor. But i get 397v b+ not 300v. I have checked my circuit msny times now and see no errors. I tried to use the psu designer software to run a simulation but i just get an error when i hit tge simulate button. Any ides why my b+ is this high. Do i need to add a resistor?
I managed to make up a rig so that I could power it up while it was upside down with the valves in place.
I used croc clips to check voltages. So that they were on the terminals for longer.
Readings are different now.
Switch on.
B+ increases to just under 360v then slowly decreases to 200 where is stables out. At this point i have 212v at pin 8 on rectifier.
Rectifier heater supply - This ncreases to 5v snd at the same point that the b+ decreases it sags to sbout 3.8v.
At this point the mains voltage also sags down to approx 190v from 240v. This has really confused me.
At start up the speakers are silent and then they start to crackle when the voltages start to decrease. And at this point the dim bulb glows dimly. And one channel makes music all be it quietly with distorted bass.
I am getting 0.57 v at 12at7 cathode / r2 and 0.8v at el34 between out pin of lm317 and r7.
This is so frustrating. I was feeling so possitive about this build too.
Any help appreciated.
Matt
I was about to react on your post #23 with the following text:
"The description of the amplifier says the current demand of the total amplifier is a little under 100 mA at a B+ of 315 V. The 300 V - 0 - 300 V in combination with a 5R4GY at 100 mA seems OK when looking at the datasheet.
But because you measured B+ to be 400 V, probably there was hardly any current flowing. Did you measure the 400 V without the tubes working?"
But your measurements in your last post make just as less sense to me as they do to you. For B+ to drop to 200 V the current must have been very high, unless by mistake you measured something else.
Maybe it's best that you take a little bit of distance from your project for a short time, and than calmly check the connections (probably again). I've been there before myself...
"The description of the amplifier says the current demand of the total amplifier is a little under 100 mA at a B+ of 315 V. The 300 V - 0 - 300 V in combination with a 5R4GY at 100 mA seems OK when looking at the datasheet.
But because you measured B+ to be 400 V, probably there was hardly any current flowing. Did you measure the 400 V without the tubes working?"
But your measurements in your last post make just as less sense to me as they do to you. For B+ to drop to 200 V the current must have been very high, unless by mistake you measured something else.
Maybe it's best that you take a little bit of distance from your project for a short time, and than calmly check the connections (probably again). I've been there before myself...
If your 240 Volt power mains sags down to 190 Volts . . .
Either your house wiring is faulty, and it may cause a fire!
Or, your power mains company needs to fix their problem, or they may have a fire soon!
Either your house wiring is faulty, and it may cause a fire!
Or, your power mains company needs to fix their problem, or they may have a fire soon!
...mattyboy, in the opening post and post title output tube is el84 but in post no. 21 you are calling the output tube as el34. Which is right? Earlier you were claiming B+ is too high at 400v now it is sags to 200v.
As PFL200 suggested please take a break from the project. And come back with a fresh look. Try something simpler first like no feedback no solid state in signal circuit if you become successful then look again at rh circuit.
Regards
As PFL200 suggested please take a break from the project. And come back with a fresh look. Try something simpler first like no feedback no solid state in signal circuit if you become successful then look again at rh circuit.
Regards
Yes the break was needed appologies. I meant el84.
The 400v changed as it happens. I do get a higher reading on B+ between 365 & 400v depending on fluctuations in mains input I presume.
However after I managed to set up a rig with the amp upside down and the tubes in (so that I could use croc clips for longer readings with the psu \ filter circuit under load), I realised that after the initial inrush etc at switch on, the b+ dropped dramatically from 365v to around 200v where it seemed to settle. I think that this is because the el84's and 12at7 are not yet warmed up.
At the point that it settled the dim bulb 100w started to glow all be it faintly.
I realise also that my statement about mains sagging was not strictly correct. These readings were taken from the output of the variac/ dim bulb rig rather than the wall socket.
If i get time I am going to sit with the circuit tonight and carefully check continuity between components. I am going to re trace it again to check that flow and component values are correct too. I have More LM317's on order too just in case.
If i am happy with my continuity and circuit checks. I may then power it up slowly (later in the week) with the variac minus the dim bulb unit and see if this makes a difference to b+. At that point I will take more readings.
I feel better this morning having rested. And I am working on a more logical approach to try and resolve this.
Thanks
Matt
After checking my dmm batteries 🙂 I have been through the entire circuit thoroughly.
1. Checking for shorts at pins etc.
2. Checking values and placement of resistors and caps.
3. Checking pins used.
4. Checking all ground points.
5. Checking continuity
Findings are.
1. I am a numpty 🙂. I have connected one input to the cathode rather than grid on one channel. This will explain the lack of music in one channel and probably the crackling.
The bits I am unsure of are.
2. No continuity on the power transformer 300v coils (through the simple buzzer test). The transformer was producing voltage when i switched off on sunday so I assume that this is ok.
3. No continuity through tbe choke in circuit ( again simple buzzer test). I have another small Hammond choke and its the same on that one too, so I assume this is ok too.
4. I have continuity on the voltage regulator between adjust and out pins. Need to look into how they work as I am not sure that this sounds correct.
Apart from this all is good. The input rewire will hopefully be a giant leap forward, quick win
Hi
However after I managed to set up a rig with the amp upside down and the tubes in (so that I could use croc clips for longer readings with the psu \ filter circuit under load), I realised that after the initial inrush etc at switch on, the b+ dropped dramatically from 365v to around 200v where it seemed to settle. I think that this is because the el84's and 12at7 are not yet warmed up.
-Once any tube is fully warmed up it will draw max current in a class A circuit. So 'this is because the el84's and 12at7 are not yet warmed up' is not correct.
2. No continuity on the power transformer 300v coils (through the simple buzzer test). The transformer was producing voltage when i switched off on sunday so I assume that this is ok.
3. No continuity through tbe choke in circuit ( again simple buzzer test). I have another small Hammond choke and its the same on that one too, so I assume this is ok too.
-Simple buzzer test does not work beyond 10R i.e. if the dc resistance of a given coil is more than 10R the meter will not buzz.
If your mains supply fluctuate more than 5% you need to use a voltage stabilizer otherwise your tubes might lose their longevity. Other components may get damaged. Slow down and get deep breath. instead of using lm317 you may put 220R 5 watt resistor from cathode to ground bypassed with 470uf capacitor. If nothing works take rest for one week then go try to implement this : https://www.dmitrynizh.com/6p14p-set.htm
Regards
However after I managed to set up a rig with the amp upside down and the tubes in (so that I could use croc clips for longer readings with the psu \ filter circuit under load), I realised that after the initial inrush etc at switch on, the b+ dropped dramatically from 365v to around 200v where it seemed to settle. I think that this is because the el84's and 12at7 are not yet warmed up.
-Once any tube is fully warmed up it will draw max current in a class A circuit. So 'this is because the el84's and 12at7 are not yet warmed up' is not correct.
2. No continuity on the power transformer 300v coils (through the simple buzzer test). The transformer was producing voltage when i switched off on sunday so I assume that this is ok.
3. No continuity through tbe choke in circuit ( again simple buzzer test). I have another small Hammond choke and its the same on that one too, so I assume this is ok too.
-Simple buzzer test does not work beyond 10R i.e. if the dc resistance of a given coil is more than 10R the meter will not buzz.
If your mains supply fluctuate more than 5% you need to use a voltage stabilizer otherwise your tubes might lose their longevity. Other components may get damaged. Slow down and get deep breath. instead of using lm317 you may put 220R 5 watt resistor from cathode to ground bypassed with 470uf capacitor. If nothing works take rest for one week then go try to implement this : https://www.dmitrynizh.com/6p14p-set.htm
Regards
I am also having issues getting a new point-to-point wired project going which incorporates semiconductors, and it does add another level of complexity since it can be hostile in there for them, and it is not as easy to test those parts of a circuit, as it is to power up slowly and measure voltages at pins. My one is using a CCS on the cathodes of the drivers.
The suggestion here to use a cathode bias resistor on the EL84 as a temporary measure, maybe just on one channel, would make the circuit a bit more tolerant, and give you confidence the OPTs were wired correctly, and then when you are happy, you could switch back.
I'm considering a similar approach with my issue.
The suggestion here to use a cathode bias resistor on the EL84 as a temporary measure, maybe just on one channel, would make the circuit a bit more tolerant, and give you confidence the OPTs were wired correctly, and then when you are happy, you could switch back.
I'm considering a similar approach with my issue.
Went through it step by step tonight with no dim bulb and having moved input to pin 7.
First off voltages with no rectifier.
Mains - 240v
From trans to rectifier - 650v
Heaters 6.3 - 6.7v
Heaters 5 - 6.2v
With rectifier no amp tubes.-
B+ - ground 436v dc
1st Cap 47uf - Ground 446v
Mains 240.
I was gonna quit here for tonight but temptation got me.
I put amp tubes in and raised voltage 20v at a time via the vsriac with my phone as a source playing music. No smoke or bangs, I get to 240v input and B+ is sittin nicely somewhere between 300v and 320v on both channels depending on where the knob is on the variac.
One speaker is intermittent though some times crackles other times music. When it plays music both channels sound good no distortion.
Bad tube I thought with my fingers crossed as I know thst somewhere i have a bad el84 that i havent thrown out yet. Unfortunately not, as I swapped them and I get the same results. I am pretty sure 12at7 is good as I use it in my Tubelab sse.
Anyway looks like the power issues were the dim bulb tester after all. Another mystery solved. So basically I just have to clean up the other channel now. I think that it must be a LM317. One thing I notice is tast the tube that is on the faulty channel isnt as hot as the other one. I wired one el84 and a 12at7 onto one 6.3v winding 1.5a and the other el84 to the 1.0a 6.3 winding. I wonder if yhis is causing any issue.
Going to check all joints 1st and possibly reflow one or two, as this seems likely too.
Matt
First off voltages with no rectifier.
Mains - 240v
From trans to rectifier - 650v
Heaters 6.3 - 6.7v
Heaters 5 - 6.2v
With rectifier no amp tubes.-
B+ - ground 436v dc
1st Cap 47uf - Ground 446v
Mains 240.
I was gonna quit here for tonight but temptation got me.
I put amp tubes in and raised voltage 20v at a time via the vsriac with my phone as a source playing music. No smoke or bangs, I get to 240v input and B+ is sittin nicely somewhere between 300v and 320v on both channels depending on where the knob is on the variac.
One speaker is intermittent though some times crackles other times music. When it plays music both channels sound good no distortion.
Bad tube I thought with my fingers crossed as I know thst somewhere i have a bad el84 that i havent thrown out yet. Unfortunately not, as I swapped them and I get the same results. I am pretty sure 12at7 is good as I use it in my Tubelab sse.
Anyway looks like the power issues were the dim bulb tester after all. Another mystery solved. So basically I just have to clean up the other channel now. I think that it must be a LM317. One thing I notice is tast the tube that is on the faulty channel isnt as hot as the other one. I wired one el84 and a 12at7 onto one 6.3v winding 1.5a and the other el84 to the 1.0a 6.3 winding. I wonder if yhis is causing any issue.
Going to check all joints 1st and possibly reflow one or two, as this seems likely too.
Matt
Please compare lm317 device wiring between good and bad channel. If nothing works replace lm317 with 220R 3/5 watt resistor.
Please Remember:
1. Tubes are much more tolerant than solid state.
2. Unloaded circuits give B+ bump, check if all capacitor voltage rating is high enough.
3. At switch on tubes heaters are cold and B+ is high, it takes about 30 seconds to settle B+.
4. When building a new tube circuit it is a good practice to write pin numbers just adjacent to actual tube pins.
Also please check:
1. Rectifier heater/filament voltage
2. Input/driver tube heater voltage
3. Output tube heater voltage
1. Rectifier plate and cathode voltage
2. Input/driver tube plate and cathode voltage
3. Output tube plate and cathode voltage
Your output transformer voltage ration is about 1:30 so if you put 220 volt AC at primary secondary voltage will be about 7 volt. If any problem you can disconnect the OPT from the circuit and test this way. For this you should consider end to end wire for primary and secondary. I usually connect winding start wire with positive terminal and end wire with ground. If your OPT is not marked already it is difficult to say which wire is winding start and vice versa.
Congratulations, you are almost there. When it will be playing beautifully you will be rewarded with great happiness. Please keep us posted.
Regards
Please Remember:
1. Tubes are much more tolerant than solid state.
2. Unloaded circuits give B+ bump, check if all capacitor voltage rating is high enough.
3. At switch on tubes heaters are cold and B+ is high, it takes about 30 seconds to settle B+.
4. When building a new tube circuit it is a good practice to write pin numbers just adjacent to actual tube pins.
Also please check:
1. Rectifier heater/filament voltage
2. Input/driver tube heater voltage
3. Output tube heater voltage
1. Rectifier plate and cathode voltage
2. Input/driver tube plate and cathode voltage
3. Output tube plate and cathode voltage
Your output transformer voltage ration is about 1:30 so if you put 220 volt AC at primary secondary voltage will be about 7 volt. If any problem you can disconnect the OPT from the circuit and test this way. For this you should consider end to end wire for primary and secondary. I usually connect winding start wire with positive terminal and end wire with ground. If your OPT is not marked already it is difficult to say which wire is winding start and vice versa.
Congratulations, you are almost there. When it will be playing beautifully you will be rewarded with great happiness. Please keep us posted.
Regards
This is so odd. I re flowed 3 joints on the noisy channel tonight. Check for shorts with the meter etc and then decide to start it up. Right channel perfect left channel just horrible crackling and noise. I get my bamboo chop stick and start prodding. At the point that i tap the 240r resistor from the el84 grid, the noise stops. I then continue to tap it and the noise stays away. I then get excite and take it in the lounge to connect it to my system. It sounds superb, but every now and then i get a crackle or pop on tbe same channel. Is it possible that the 240r resistor is faulty? I am very surprised how much bass those little OPT's produce compared to my 5kg hammonds in the SSE there is not a whole lot of difference. Very surprised. This is very nice sounding though.
240R grid stopper resistor should be connected between grid and .22uf coupling cap. 470k grid leak should be connected from junction point of 240R and .22uf coupling cap to ground. Any of these might be faulty. Replace them one at a time and see what happens.
Please check heater voltage of all the tubes, this is also very important.
Regards
Please check heater voltage of all the tubes, this is also very important.
Regards
Not sure what tube sockets you are using but you may be losing connection to the grid pin on your tube.
It's possible that sometimes you can tighten the contacts.
Ok will try and check this. How do I tighten them Just standard B9a, porcelain ones from HiFi Collective.
Just a thought. Are grid stoppers supposed to be right next to the valve pin? Mine is not. It's about an inch away. It is metal film too.