Drip 670 V2 - SOLVED

[sr1200]

My previous question regarding a transformer was for this beast of a kit.  A good friend of mine bought the whole shebang and I've been putting it together over the course of the last year.  I meticulously stuffed the board and triple checked for errors (even had my friend check for errors as well, none found)

Here's the trouble.  As soon as you put audio tubes (6386 JJ's btw) on BOTH sides of the board, (could be one tube on each side or 4 doesnt matter)  the B+ drops like a rock.  I can put 4 tubes on one side and the voltage stays stable, however, im getting a REALLY high reading of 40v at C201/202 (C101/102 it follows sides)  Once the voltage takes a dive, the voltage adjust pot is useless, i can crank it and i get no change.

I have verified that all the transformers are wired correctly and nothing is grounding out (unless theres a problem in one of those cans that i can't see)

Here are some readings that I have taken at various points on the board with the voltage stable and tubes in a single channel (again, voltages are the same on both sides until i tube up both sides):

R316 we get a reading of 143V but we should be reading 154
R131 reading -17 but supposed to be -12
R233 seeing 143V but supposed to 154
R301 reading -24. Should be -17 to -19
R302 reading -17.5 but should be -13 to -14.5
6.2 test pin reads 6.8

R301 we have 500 ohm in there. The board and one of the manuals says to make that a 1k resistor but the additional notes stated to make that 500 ohm if the voltage was too low.  (the resistor was suggested by greg over at drip at the time of purchase, i DO have a 1k 2watt metal film resistor laying around that i can pop in there temporarily if someone thinks this might be the problem)

R106/206 is the meter adjust resistor. Right now we have the 4.7k resistor that came in the kit.  Manual says we might need to toss a 10k pot in there to adjust.

There are solid (tested)grounds to star points (one on the power side, one on the XLR side) Signal ground,  Control amp ground and power ground.

I anyone has some insight into this I would be eternally grateful... I really wanna get this thing out of my shop, i think its making one side of my house sink into the ground...

oops forgot to include a link to some pics of the build (after we had to start tearin wires out to trace this problem down).
https://www.dropbox.com/sh/73y955rj7akd76l/AAAKu22BZQe_RL5c2V-EnRGia?dl=0

 

[Evertide]

Are you sure it does not matter witch tube is where ,  and this on both sides ?

 

[Evertide]

I started in 05 ...

What is the voltage on L301 ?

Whithout the tubes ( and the caps emty ... ) you can measure the resistance of the audio transformers . ( no shortage ... )

 

[PRR]

On another thread you were fretting over the VAC off your PT.

> R316 we get a reading of 143V but we should be reading 154

As I can't find the Drip schematic, this may as well be the EGR valve on my Honda.

It appears you are measuring deep "inside" the signal stages.

> B+ drops like a rock.

So work *through* the power supply, from rectifier and first filter cap, and document what you got at each point.

No point looking under the sink if the real problem is a bad valve where water comes into the house. While puncturing pipes to check pressure at each joint is awkward, electric voltage is real easy to probe all along the pipe (supply filter chain).

 

[sr1200]

First, thanks for the replies

Drip Documents:
https://ws.onehub.com/folders/cydcrgff (v2)
https://ws.onehub.com/folders/a1yfdu1d (v1 which has way more info than v2 including the schematics in the drip 670 manual document starting on page 269)

It doesnt matter where i have the tubes. we tried one tube on one side, ok, one tube on both sides, voltage dives.  4 tubes on one side, ok.  4 tubes on one side and ONE on the other, dives.

Im getting almost 25v at r301 which is why i think maybe the 1k is a better option there since the 500ohm was supposed to be if the voltage there was LOW, we're a bit high.  Could this throw everything else out?

When i checked the AC on the pt i was getting the out of phase thing happening so i thought, maybe im only getting half the power im supposed to or something, but that turned out NOT to be the case. 
With only the power tubes in everything is within spec limits (20% according to greg) with r301 being a bit too hot because of that resistor.  It's only once the audio tubes are in does everything start going to hell.  We tried powering up adding a tube at a time in the controller section and everything was stable throughout that.  There isn't much to the power section.  We're not using the selenium rectifier.

Again thanks so much for the eyes on this.  Drivin me bananas!

 

[PRR]

> everything is within spec

We are looking for clues. Maybe subtle clues. "423V" is much more specific than "within spec".

The v2 schematic is impossible for my eyes. The other is cut-up and cut-off over several pages.

PT, some kinda rectifier bottle, then both ends of L201 choke. EL34 regulator trimmed to 240V.

WHAT voltages at each point of L201 and EL34 plate and cathode? With one "audio tube" (do you mean the 6336s?) and 4+ "audio tubes" (whatever causes your "go to hell" condition)?

 

[Evertide]

How does the voltage look like ?  ( oscillation )

 

[sr1200]

specific voltages that were listed on the first post is what my "within spec" comment was referring to.
the schematic in general hurts my head as well, the whole manual makes me want to cry, everything is just all over the place.
the tubes that start the "fun" is the 6386's (there are 8) greg calls them the audio tubes I will take readings once its on the bench again.
as for what the voltage looks like, i will have to fire up the scope when i get someone to lift it back on to the bench (just had spinal surgery a month ago, no way i can lift this beast)

again much thanks for the replies.

 

[Evertide]

All tubes only in channel A all fine , all tubes only in channel B all fine ? Good sound ?

L 301 = 1172 = 68 Ohm  ,  L 302 - 1221 = 86 Ohm  ?

 

[sr1200]

yes to the tube situation.  not sure what you're asking about 301 and 302 though.

 

[Evertide]

You did not mix L 301 and L 302...

 

[sr1200]

We removed the board, completely resoldered everything.  Replaced the 500 ohm resistor with the 1k resistor at 301 (voltages are now spot on there).  Still got the high 40v at c201/202 (single cap)  we're supposed to be getting 14v.

 

[Evertide]

What are the voltages on both ends of L 301 and L 302 ?  ( with and without all tubes )

 

[sr1200]

Going to be putting the beast back up on the bench this weekend.

I got a message back from brian at sowter regarding the transformers.

He said i should check the dc resistance of each winding.  The dc resistance is normally between 5% and 10% of the nominal impedance.  I have no clue what he means by this.  If out of circuit, what would the nominal impedance be?  I was thinking of just hitting  a pair of the wires with a DMM.  Might anyone care to explain this to a dummy?  Thanks

 

[PRR]

> If out of circuit, what would the nominal impedance be?

The number printed on the can or on the sell-sheet.

"600 Ohms" is likely to read 30 to 60 Ohms on a common ohmmeter.

 

[Evertide]

All transformers are working with Alternating Voltages ( 60 Hz AC / sound ; mostly measured at 1 kHz )

With a DMM ( on resistance ) you are ( quick ) measuring Direct Voltage / Direct Current = Direct Resistance .

The nominal given resistances are Alternated ( impedance ) , so your measurements will never be exact ...

Main reason for the quick measurement is exclusion of shorting and interruption ; almost zero / infinity ( everybody makes mistakes ... ) or a measurement  ...

 

[sr1200]

Well... mission complete.  There was a bit of a miscommunication with the manual.  There were a pair of wires that needed to be run for the plate that weren't there.  As soon as we put those wires in the whole unit worked perfectly.  I appreciate the eyes on it everyone... what a pain!

 

[Evertide]

Just a simple connection...

Good-luck on your next one!

Still working on my project...

 

[Jonbjornstad]

Hey Cool to hear that you solved this. Do you remember what wires that were wrong in this case?
I just finished my 670 v1 today (AND it is compressing!!!) but I am getting on with v2 now and want to know about every trap that exists so I can avoid it myself

What a cool build

 

[sr1200]

honestly, skip 2 and go to 3 if you can.  2 was a pain in the rear!  IF you are adding the AGC board, make sure you read BOTH manuals before populating either board as there is a lot that needs to be left out on the main board for the daughter board to work properly.
I had someone bring a v2 to me for repair last year sometime, and was pulling my hair out trying to find out why that unit didn't work... turns out the guy that built it used really bad wire from the board to the front panel.  Once rewired, it worked fine.