dogears wrote:I have no idea what you refer to. The initial dropping resistor occurs after the screen caps which is after the main caps. Do you mean the balance resistors? Dumble used mainly 270K, although I have seen 220K there.
makrisp wrote:
Let me re-phrase and thank you for the correction as that is what happens when you rush w/ statements:
The power resistors related to the intial power caps, or initial dropping resistors.
Scott,
Do you mean the balance resistors? Yes, playing with those values up or down can make a heck of difference.
Yeah... I 'd definately lower the 330K that are there now. Most have 270K, but I have seen a really good one (100watter, EL34, Musicman Iron, 50UF total mains) that had 220K on there.
makrisp wrote:
Scott,
Do you mean the balance resistors? Yes, playing with those values up or down can make a heck of difference.
dogears wrote:Paul, The Dumbleator runs about 230V on the recovery amp and not 255V. I have lots of research on that matter. You are correct about the cathode voltage. 255V is about right. However, some Dumbleators dramatically changed the bootstrap values to double the cathode voltage to over 30V. Sounds better to me. I have lots of pictures of several different Dumbleators with accompanying measurements. I think the dropping string needs some mods. Up the 10K to something like 15K or more. Then up the dropping resistor to the pin 1 cathode follower side a little too, maybe to 22K.
Also, Mat's V1 and V2 voltages are in the ballpark (assuming that V2A is really 205 and not 105). This is an HRM and not an early 80s like yours. Of course, trying something a tad lower is a good idea but IMHO not the source of his issue. I personally have lots of time on a real one that I have been in.
The PI voltages are different because Mat is using the Bluesmaster PI that Dumble switched to in his later years. Same as in Carlton's amp, among many others. Still his voltages are whacked here. He should have another 40V on his PI pin 6. This PI has lower voltages and when working right sounds amazing.
I am confused about why there is a 7V difference between pics 3 and 4 on the outputs. Maybe there should be a 1 to 2 volt differential. Something seems wrong here?? Maybe the 1K choke replacement resistor is WAY too big. I'd go to a 330 ohm. I have tried 1K and it did not work at all for me. Bad tone......
makrisp wrote:
Look at the values in ( ) Get them as close as possible.
Also, Mat's V1 and V2 voltages are in the ballpark (assuming that V2A is really 205 and not 105).
Scott, I thought he was running at 105 volts, which as you know is way off.
The PI voltages are different because Mat is using the Bluesmaster PI that Dumble switched to in his later years. Same as in Carlton's amp, among many others. Still his voltages are whacked here.
( I totally agree, they are a mess)
He should have another 40V on his PI pin 6. This PI has lower voltages and when working right sounds amazing.
dogears wrote:You have much too much voltage on the recovery amp of the loop. Shoot for about 220V.
Ok.
Obviously, you have an issue with your tonestack. I bet when you fix it, the amp improves
This is strange. The pot measures to groud 1.7R-239k. The connection between the pot and .01 mid cap ok. The mid cap measures in circuit 13n8. The 150k coming to the mid cap measures 149k. The connections and the values seems to be just right. Strange..
What I really would like to do is remove the R/J switch from the circuit (which I neber use anyway). Then I would maybe understand the circuit better and it would be much easier to compare it to the 101HRM schem. Anyone could advice how to do it on the layout I posted few posts earlier ?
Good idea Mat! Get rid of the R/J switch. Fwiw, the Glaswerks doesn't have it.
Also, please lower the choke replacement resistor alot. 1K is way too large. Just put a 500ohm or 470ohm screen resistor across it in parallel! That is easy and works!
dogears wrote:Good idea Mat! Get rid of the R/J switch. Fwiw, the Glaswerks doesn't have it.
Ok, if I just would knew how to do it Ok, I'll try to search the forum and read and learn and read and...
Also, please lower the choke replacement resistor alot. 1K is way too large. Just put a 500ohm or 470ohm screen resistor across it in parallel! That is easy and works!
I had earlier 470R in there and liked it. I just wanted to hear what kind of effect the 1k would give. Too muffled kind of sound. I'll put in the parallel one
Up the 10K to something like 15K or more. Then up the dropping resistor to the pin 1 cathode follower side a little too, maybe to 33K or so.
Ok. Actually the 30k is 39k. I put in about 42k.
Also, Mat's V1 and V2 voltages are in the ballpark (assuming that V2A is really 205 and not 105).
Yes, it was a typo. 205V on V2A.
He should have another 40V on his PI pin 6
I'll try again if swapping a tube changes the voltages.
I am confused about why there is a 7V difference between pics 3 and 4 on the outputs. Maybe there should be a 1 to 2 volt differential. Something seems wrong here?? Maybe the 1K choke replacement resistor is WAY too big.
The amp was on with the choke when I measured the voltages. I'll try again with different output tubes. I'll change the EL34's to KT66's.
Yeah... I 'd definately lower the 330K that are there now.
I have 220k's on the main power caps.
Am I right on the following:
D-lator voltages should be:
pin1: 255V (I have 317V)
pin3: 30V or more (I have 41V)
pin6: 220V-230V (I have 248)
I have to go and watch the tv for while - too much solder fumes and voltage ratings and r/j switch schemes on my head right now
I measured the voltages this morning again and the PI gave 241 instead of the 211 ?
Then I tweaked the d-lator dropping resistors and finally got 245,225 in there. The power tubes (still the EL34s) also gave pin3=479 pin4=474
The sound was MUCH better
Then the PI gave again 211V ?? I changed the PI tube and got 220V. I'll change the PI soscet immediatly + measure the voltages one more time.
I have earlier disconnected the d-lator but not the power supply that goes to d-lator tube. It was not the cure. After today correcting the voltages the amp plays much easier and sound quite good
Dogears and funkalicousgroove have been more than right suggesting more filtering/external d-lator
I suspect that once you get the PI back up, the sound will be perfect! Keep us posted.... Btw, did you change the Dumbleator bootstrap values like I suggested? 27K/1.8K instead of 10K/1.5K. This will bring the pin 3 voltage up to the 30V range.
mat wrote:I measured the voltages this morning again and the PI gave 241 instead of the 211 ?
Then I tweaked the d-lator dropping resistors and finally got 245,225 in there. The power tubes (still the EL34s) also gave pin3=479 pin4=474
The sound was MUCH better
Then the PI gave again 211V ?? I changed the PI tube and got 220V. I'll change the PI soscet immediatly + measure the voltages one more time.
I have earlier disconnected the d-lator but not the power supply that goes to d-lator tube. It was not the cure. After today correcting the voltages the amp plays much easier and sound quite good
Dogears and funkalicousgroove have been more than right suggesting more filtering/external d-lator
dogears wrote:I suspect that once you get the PI back up, the sound will be perfect! Keep us posted....
I hope so Sure, I will make clips as soon as it is running properly
Still haven't figured out the mid-pot-bug
Btw, did you change the Dumbleator bootstrap values like I suggested? 27K/1.8K instead of 10K/1.5K. This will bring the pin 3 voltage up to the 30V range.
,but I did not have a chance to play the amp - we got a power brake down First I thought it was my build But when I got to work all the traffic lights were down also
,but I did not have a chance to play the amp - we got a power brake down First I thought it was my build But when I got to work all the traffic lights were down also
Mat,
Try and balance the PI as both sides are far appart, P1=274, P6 =246.
Get them closer to 274 volts, or as I stated earlier 300Volts on each.
You can't get 300V with the style PI Mat has. Anywhere in the 240-270V rage is normal. I get about 10V between sides. It is not about the volts but the AC balance...
makrisp wrote:
mat wrote:I had time this morning to measure some of the voltages with the new tube socket (tubes fit in very sturdy):
,but I did not have a chance to play the amp - we got a power brake down First I thought it was my build But when I got to work all the traffic lights were down also
Mat,
Try and balance the PI as both sides are far appart, P1=274, P6 =246.
Get them closer to 274 volts, or as I stated earlier 300Volts on each.
You can't get 300V with the style PI Mat has. Anywhere in the 240-270V rage is normal. I get about 10V between sides. It is not about the volts but the AC balance...
I adjusted the trimmer and got minimum of 20V difference on the PI plates, good enough ?
The mid cap problem also solved. I had soldered in mistakenly 10n on the bass pot (also in the layout) while should have been a 1n.
Dogears, I have two spare dpdt's on the back panel and was wondering what cap/resistor would be good to have switchable when using a telecaster with this kind of circuit. I would like to shoot for the Robbens tele sound (which is marvellous on the new CD). I have read that changing the mid cap would be a start. Would that be enough ? Robbens tele sounds really nice and fat to my ears.
For now I have deep and V2 snubbers behind the switches, but the snubbers makes the sound kind of dull to me. I'll get rid of those. As for the deep switch, I'm not sure yet. Have to listen more.
I have milder mid boost (as in the layout) would You suggest the normal circuity for the BM-style amp ? (of course I'll listen to it but would be nice to know how You feel about it).
My bright switch is also 3 position. 270p, off, 100p.
You can't get 300V with the style PI Mat has. Anywhere in the 240-270V rage is normal. I get about 10V between sides. It is not about the volts but the AC balance...
makrisp wrote:
mat wrote:I had time this morning to measure some of the voltages with the new tube socket (tubes fit in very sturdy):
,but I did not have a chance to play the amp - we got a power brake down First I thought it was my build But when I got to work all the traffic lights were down also
Mat,
Try and balance the PI as both sides are far appart, P1=274, P6 =246.
Get them closer to 274 volts, or as I stated earlier 300Volts on each.
Employ a trimmer pot to balance the sides.
Scott,
Why can he not increase or decrease the resistiors within this section, so that he can either increase or decrease the voltage?? The PI resistors, pins 1 & 6, usually a 100K & 82K for a typical Fender can be adjusted up or down to decrease or increase the voltages at those points. I usually play with those resistors to get the voltages where I want them and then employ a trimmer to balance them almost perfectly.
Are you coming to Boston next month for the guitar show at Bayside Expo Center?
You can stay at my home, I have a couple of extra bedrooms, I will even allow you to sleep next to the Dumble!
Ok, I'll try to search the forum and read and learn and read and...
