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Need help/advice:
My Audio Research VS 110 sounded off, so I checked the bias and V5 was getting no reading. The tube was glowing, but wasn't nearly as hot as the other output tubes. The over 6550's were at the proper bias. I tried other tubes in V5 and still no readings.
Dilemma, I'm in Chico, CA, there is only one place that works on tube gear and primarily guitar amplifiers. I'm waiting to hear back from Kelvin from ARS to see what he suggests.
There is a repair place in Sacramento, which would take at least a month or more, not to mention driving there twice.
My question, is it just a resistor causing the problem, or possibly something else? I haven't talked to the guy locally who works on tube guitar amps, but he was recommended by a local audiophile.
Help!!!
Thanks,
Jim
ARS VS-110
Customized Bottlehead Foreplay II Preamp
Magnepan 2.5R's
B&W ASW 300 Subs
Ah Troeb Tube CD player
MaggieMate X/O's from subs to 2.5R's
Follow Ups:
BigJim needs an amp that's hand wired like a tweed Bassman.
Loose the AR, build your own with advise from the DIY forum.
Or trade me some expensive firewood, and I'll do it for you,
I'm only a few hours from Chico.
Oh yes indeed, nothing like a hand wired, point to point Bassman
ARS VS-110
Customized Bottlehead Foreplay II Preamp
Magnepan 2.5R's
B&W ASW 300 Subs
Ah Troeb Tube CD player
MaggieMate X/O's from subs to 2.5R's
Well why don't you get busy and either make or come up with a hand wired point to point audio amp ? duh ?
Sell that 66 LPB bolt on neck thing, and fund the project. Keep the bassman, of course.
BTW though, I built a homebrew 5F6-A head, so I could get my '58 bassman back from a great player I loaned it to, and we both thought the head
was equal if not a little ballsier. It cost about $300.....
Simple answer, the VS110 sounds wonderful. I love DIY, just don't have the time anymore to take on a project, especially a high wattage tube amp. That 1966 strat is a friggin tone machine😎.
Jim
ARS VS-110
Customized Bottlehead Foreplay II Preamp
Magnepan 2.5R's
B&W ASW 300 Subs
Ah Troeb Tube CD player
MaggieMate X/O's from subs to 2.5R's
.
wired back to AA864 is no slouch, either. 8^)
.
.
There's a 90% chance that there is an open resistor in either the cathode of V5 or the screen grid of V5..Either of these resistors being open will cause the tube not to conduct and therefore not bias up.
It's very easy to check to see if the screen grid voltage is at pin 4 where it needs to be..Pull the tube out and measure the DC voltage at pin 4 with the meter's black lead going to the chassis..You just need to be over 400vdc.
The cathode resistor you check by doing what Tre said..Measure the resistance from pin 8 of V5 to ground.It should be 10 ohms or less depending on which value they used.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
Edits: 02/18/15
I s/w Kalvin today (Audio Research) and he said most likely the tube arc'ed during warm up. I ordered both resistors and will bias in a new tube once I put the resistors in.
Jim
ARS VS-110
Customized Bottlehead Foreplay II Preamp
Magnepan 2.5R's
B&W ASW 300 Subs
Ah Troeb Tube CD player
MaggieMate X/O's from subs to 2.5R's
Thanks to all. No doubt it is an open (shorted) resistor, since I work too many hours, it will be a day or so before I figure out which or if both are bad. Sounds like I don't need to worry to much and the guy locally ( after I talk with him and feel more comfortable about his ability), will do the repair as I don't have a suitable work bench at my new abode.
Thanks again,
Jim
ARS VS-110
Customized Bottlehead Foreplay II Preamp
Magnepan 2.5R's
B&W ASW 300 Subs
Ah Troeb Tube CD player
MaggieMate X/O's from subs to 2.5R's
Jim
Just open in this case because if they were shorted,it would still bias...Both resistors in this case are more or less protection devices.
Harman Kardon and Mcintosh always used the screen resistors and they were there mostly to protect the wonderful output transformers.In the case of the cathode resistor,it also aids in measurement for bias.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
Never worked on PCB's. Using V4 as the example, were are the resistors for socket 4/8 located, i.e., on the bottom of the PCB or on top?
Jim
ARS VS-110
Customized Bottlehead Foreplay II Preamp
Magnepan 2.5R's
B&W ASW 300 Subs
Ah Troeb Tube CD player
MaggieMate X/O's from subs to 2.5R's
Jim
You can handle this.They are using a 1 ohm cathode resistor which is perfect for direct measurement. The 100 ohm resistor is what feeds the screen grid..Just go to V5 and change those resistors along with the bad tube and you should be good to go.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
Nt
ARS VS-110
Customized Bottlehead Foreplay II Preamp
Magnepan 2.5R's
B&W ASW 300 Subs
Ah Troeb Tube CD player
MaggieMate X/O's from subs to 2.5R's
The two larger resistors, one to the left and one to the right of the tube socket, are the two 1 ohm resistors that connect to the plate (pin 3) and the cathode (pin 8).
There should be a 100 ohms screen grid resistor as well(the screen grid is pin 4). That one is probably under the board. I would guess it is connected to the traces just to the left of the "v4" on the picture.
You should measure them all with a ohm meter or just change them all and the tube.
BTW Looking from the top, pin one is to the left of the key-way, pin 8 is to the right of the key-way.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Thanks to all. The 1 ohm was fried and its on the bottom of the board. To be safe, I also changed out the 4 pin 100 ohm. Will be firing her up in a bit and rebias. Hoping all is good.
Jim
ARS VS-110
Customized Bottlehead Foreplay II Preamp
Magnepan 2.5R's
B&W ASW 300 Subs
Ah Troeb Tube CD player
MaggieMate X/O's from subs to 2.5R's
I need to get my eyes checked.
The two top resistors look like black, brown, black to me.
100 ohm would be brown, black, brown.
Good work. I'm glad you found it.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Drat:
Didn't fix it😤....will run it half power until I can drive it to Sacramento.,,,
Jim
ARS VS-110
Customized Bottlehead Foreplay II Preamp
Magnepan 2.5R's
B&W ASW 300 Subs
Ah Troeb Tube CD player
MaggieMate X/O's from subs to 2.5R's
On of the beauties of tube amplification is that you can bypass the hurt part and run them at half power. In the case of my VS110, it sounds amazingly good at half power even with Magnepan's.
Will get a thrift store amp (yuk) and then drive the ARC to Sacramento to be properly diagnosed and fixed.
Jim
ARS VS-110
Customized Bottlehead Foreplay II Preamp
Magnepan 2.5R's
B&W ASW 300 Subs
Ah Troeb Tube CD player
MaggieMate X/O's from subs to 2.5R's
to having it fixed.
The resistor under the board is the 100 ohm screen grid resistor. I can see that from the picture. It connects to pin 4. The two resistors on top are the 1 ohm resistors. One for the plate and one for the cathode. Did you check them?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Tre...
I will give it another try tomorrow, I must have misunderstood the advice a guitar amp tech gave me. I put the damn 100 where the 1 goes and visa versa. Simple fix and hope it gets me back to full power😎.
Thanks to everyone for hanging in there with me.
Jim
ARS VS-110
Customized Bottlehead Foreplay II Preamp
Magnepan 2.5R's
B&W ASW 300 Subs
Ah Troeb Tube CD player
MaggieMate X/O's from subs to 2.5R's
.
Have Fun and Enjoy the Music
"Still Working the Problem"
Great news, I put the right value resistor on pin 4 and replaced the original resistor on pin 8 and everything appears to be right again, it biased up perfectly with a new tube in place. Needless to say, thank you to each and everyone here who told me I could do it and helped me when I needed it the most.
Later today I will give it a nice listening session😎.
Jim
ARS VS-110
Customized Bottlehead Foreplay II Preamp
Magnepan 2.5R's
B&W ASW 300 Subs
Ah Troeb Tube CD player
MaggieMate X/O's from subs to 2.5R's
.
Have Fun and Enjoy the Music
"Still Working the Problem"
Tre:
It does feel mighty good, especially when it sounds wonderful again! Just listened to Echos (Pink Floyd) and I was in the happy zone that only a good system can take you to.
Jim
ARS VS-110
Customized Bottlehead Foreplay II Preamp
Magnepan 2.5R's
B&W ASW 300 Subs
Ah Troeb Tube CD player
MaggieMate X/O's from subs to 2.5R's
.
Have Fun and Enjoy the Music
"Still Working the Problem"
It was the 1ohm, 2watt that fried😷
ARS VS-110
Customized Bottlehead Foreplay II Preamp
Magnepan 2.5R's
B&W ASW 300 Subs
Ah Troeb Tube CD player
MaggieMate X/O's from subs to 2.5R's
Nt
ARS VS-110
Customized Bottlehead Foreplay II Preamp
Magnepan 2.5R's
B&W ASW 300 Subs
Ah Troeb Tube CD player
MaggieMate X/O's from subs to 2.5R's
First of all, that V5 tube is probably no good. Don't trust it.
The problem is probably the screen resistor. It is I believe a 100 ohm resistor. Pretty simple job to replace, just make sure whoever does it uses the same resistor type, and have them check the cathode resistor as well
Dan Santoni
If the cathode resistor on that socket is open then the only heat would be the heaters because no plate current would flow.I would open it up and check the resistance value of the cathode resistor. You might just need to change that one resistor. (and the tube, the resistor didn't burn itself up, the tube is probably shorted)
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 02/18/15
Nt
The tube has about 200 hours on it, a short should/would have raised its ugly head within a few minutes/hours. The amp is 12 years old (new for a tube amp), so I could see a resistor failing or a solder joint.
Jim
ARS VS-110
Customized Bottlehead Foreplay II Preamp
Magnepan 2.5R's
B&W ASW 300 Subs
Ah Troeb Tube CD player
MaggieMate X/O's from subs to 2.5R's
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