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alexc

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HNY to you too guavatone  :)

Hope you till some more ground in your orange86 related research this new year of '19.
 

iomegaman

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I hate to be a dunce here, but I am going through my dual O86 and cleaning up my messes (lots of bad wiring on my part, I've learned better tools and slower approach makes better results)...

Anyway, I JUST found out I had my PSU resisted to ONLY be one channel and am fixing that...

But I still have two lingering questions...

My DC heater voltage is only giving me about 4 V, not the 6.3v as advertised...I might switch to AC heaters if I cannot sort the short...where should Iook to find the missing 2.3 volts since my AC coming out of the Tranx is 6.3? Or is 4 volts close enough?

Second...I originally had the pad switch jumpered and out of circuit, even though I populated it  and wired it up...as I go and re-do the DI board I notice "SW A and SW B" going to SW-1 on schematic...and like a dufas I do not remember where the respective "A and B" are on the actual switch BUT I do have to empty pads on it...I am assuming those are "A and B" but they are not labelled...anyone know offhand if I am correct and if so which is which?

One pad is in middle of switch (I assume A) one is on edge of switch (B?)


Sec
 

guavatone

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I’m not clear on your question. Switch is A,B and C. Position A bypasses PAD. B and C are -15 and -20 respectively.

Can you tell more about the DC heater setup? Transformer specs?  Regulated? For regulated 6.3V you really need an 8-10V transformer.

6.3 x 1.414 = 8.9V leaving only 2.6V difference which a close margin for Regulators
 

iomegaman

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guavatone said:
I’m not clear on your question. Switch is A,B and C. Position A bypasses PAD. B and C are -15 and -20 respectively.

Can you tell more about the DC heater setup? Transformer specs?  Regulated? For regulated 6.3V you really need an 8-10V transformer.

6.3 x 1.414 = 8.9V leaving only 2.6V difference which a close margin for Regulators

First question: On the DI schematic you can see "SWA and SWB"  which correspond to two pads on the actual DI pcb that I originally had jumpered (as per notes on build wiring doc)because I was bypassing the Pad switch... now that I am populating the DI pcb I am asking where the two points/pads "SWA" and SWB" are to be connected to...I was assuming it is the 2-empty solder pads on the actual "PAD" board, one in the center and one on the edge but they are not labelled...and since I have soldered the switch to the board I cannot see the other side to determine which solder-pads are SWA/SWB...hope that makes sense...basically I am asking what connects o SWA/SWB on the actual DI pcb...

As far as the psu/tranx...I am using the Edcor XPWR 106...and your PSU board with the BOM tranx for the 48/24/12v ...

I did install the two 6.8 Ohm /5Watt xicon resistors recommended in the original BOM for 1-channel...(R-1 jumpered)...I might need to replace/check VR-1 it doesn't seem to do crap at all...

PS it just occurred to me, I have the original blue PCB psu , not the newer simplified ones...
 

guavatone

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Ahhhhh. OK! Check out my 1st post revision where I mention “definitive” build. I designed the DI with too many options. Other than the LED and LED resistor the DI doesn’t really need any parts. But you can put the diodes in for protection.  So number iether R1, C1 or SwA SWB. Then jump C2 and R2. Does that help?

Omit R2 on preamp and use RT of 130-150K and DI-L of 1-2 Meg

Too much Current is being drawn and the reg isn’t regulating so VR1 wouldn’t do anything.  The  transformer isn’t the one for the heater job. In my BOM I mention the values are for 10V secondary.  Not to worry though.

So math is good and necessary in these affairs. 2 channels are drawing 1.5 amps for heaters. So 4 V makes sense. And confirms all is not lost and physics is doing physics.  6.8R in parallel is 3.4R.... 3.4R at 1.47 Amps will drop 5V, which is why we are happy with your 'faulty' 4V and and you have little to worry about .  Let’s compromise and ditch the regulator and drop the heater voltage with simple resistance.

We want approximately 1.7 ohms to get us from 8.9V to 6.2-6.3VDC

8.9-6.3=2.6
Ohms Law 6.6V/1.5A = 1.7 Ohms

A 3.9 and 3 ohm in parallel will get us very close to 6.3V when under the full 1.5Amp load.  Just make sure you have all 4 heaters hooked up in this configuration. And just solder jumper wires from Regulator input and output.  and remove protection diodes and adjustment circuit resistors and VR-1 and you should be up and running or at least heating.

So the following parts are under $2 rather than buying a new transformer

https://www.mouser.com/ProductDetail/Ohmite/TWW5J3R0E?qs=sGAEpiMZZMsPqMdJzcrNwsjn3H8PIsuRxJWLCSajA2M%3D

https://www.mouser.com/ProductDetail/Ohmite/TWW5J3R9E?qs=sGAEpiMZZMsPqMdJzcrNwsjn3H8PIsuRN3RHxa7LWeM%3D
 

iomegaman

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Thanks  :D

Will give it a shot and report back later...I'm re-wiring the gain switch right now and of course had to rebuild my pace removal iron and then defaulted to wire wick instead...somethings work because they have always worked...not all advances in technology move us forward.
 

guavatone

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Iomegaman.  Before you finalize the resistor values, what else is drawing current from the LT(6.3V)? Do you have there n'off indicator hooked up to it? bc it seems a bit more draw than usual.

Also. Please measure the voltage across the  6.8 Ohm resistors so we can confirm the correct dropping resistors for the job.

 

iomegaman

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Yes there's an indicator lamp I'm going to take out of the circuit and get some readings...looks like it had 32k resistor going before the filament...
 

iomegaman

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Took the lamp out of the circuit, putting everything in a new case, wired up PSU/Tranx/On switch...getting 6.8 DC off the board now under no load...gonna wire everything else up and give it a spin...

Put it in a shallower case with the main Tranx off the back instead of inside gotta drill some holes for XLR's mount switches/input/output-tranx/DI/etc...hope to have it tested later...
 

guavatone

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With the 2 6.8R resistors you’ll get around 3 volts. The heaters draw about 1.1 Amps. I forgot about diode drop as well because I have  been doing HV design and it’s a moot point.  But at that under 10V range it becomes a nuisance.  But that reading makes sense if you are using diodes with a 1V drop at 1 Amp.

What rectifier diodes are you using? A common way to do this is use Schottky diodes with only .4-.5 Vf drop.

You can try without the dropping resistors and run the heaters a bit hot and modify later. It’s a tad high but i’ve Been running my V72’s at just under 7 volts ( 122V mains) for years with no problems and still sound great.
 

iomegaman

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Hey just another meandering question:

I notice in picture of the "mod" where you install a couple of caps across V1 grid/R8 mod that there is another cap across :

V1  K (4^5)

...what are you running there and why? Is that for noise or oscillation? Looks like  a high frequency cap of some sort?
 

guavatone

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iomegaman said:
Hey just another meandering question:

I notice in picture of the "mod" where you install a couple of caps across V1 grid/R8 mod that there is another cap across :

V1  K (4^5)

...what are you running there and why? Is that for noise or oscillation? Looks like  a high frequency cap of some sort?
I was doing some test in HD recording at 96K and didn't like the HF response.  I found that the HF stuff was coming from the gain switch caps that cut HF by a boosted Negative Feedback high Frequency signal.  when measured on the AP it sure enough showed jagged edges rather than a smooth rolloff.  So rather than using Feedback to cut highs, we'd rather cut them a bit at the input.  And at low feedback settings(higher gain) there was some HF loss.  This is the nature of Negative feedback.  When you add Negative feedback bandwidth increases.  Remove Negative feedback the inverse occurs.  So the cap across R8 is to compensate for this.  Shall we call it a compensation cap?  So with the 22p-33p cap across R8 with the Constant Impedance Gain Switch, we get fairy flat response to 20K.  And with the High cut at V1's input we get lest phasing from the old gain switch.  By "K (4^5)" do u mean KiloVolts? 

Ideally though we want a 120-220p cap at the input transformer secondary and a 20-47p cap at V1's grid so that the DI does not suffer so much HF rolloff.  I hope to add that soon.

Does that help?
 

iomegaman

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Kilovolts, No I was talking about the little brown capacitor across Heater filament, (not sure why  I was thinking its "K" it s "f") ...pins 4 and 5 on V1 tube itself...if you look in the pic you provided its up in the top left...I believe it goes across the 6.3 heater supplies...
 

iomegaman

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So my voltages seem to be all tube dependant...

ALL MEASUREMENTS FROM TOP OF PCB:

No tubes:

V1
1.  284
2.    0
3.  0
4.  0
5.  6.61
6.  300v
7.  0
8.  0
9.  0

V2

1. 304
2. 0
3. 0
4. 0
5. 6.61
6. 305
7. 0
8. 0
9. 0




NOT SURE WHERE I HAD THE GAIN SWITCH SET TO SO THESE NUMBERS ARE POINTLESS...

V1 (Electro Harm EF-86) (Russian 6X/J32N)

1.    284....286
2.    0....0
3.    0 ....    1.63
4. 0/0
5.    6.62.....4.42
6.  300.......84
7.    0/0
8.  0.........1.63
9.  0/0

V2  (JJ E88CC)    (Ruskie 6H1N-be careful what you buy on ebay!)

1.  304                  119
2.  0                          0
3.  0                        4.40
4.  0                          0
5.  6.61                  4.51
6.  305                  114
7.  0                        3.5
8.  0                      4.6
9.  0                        0


Gain switch with 13K across V1/V2

V1-Electro Harmonix  EF86/    V2 -JJ E88CC
        V1                V2
1.  150/            196
2.    .06                .15
3.  1.25              2.56
4.  0                    .004
5.  4.56              4.6
6.    138                193
7.    -1                      0
8.    1.26                2.64
9.    -.4                    .06
 

guavatone

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It’s really not a good idea to test without tubes in because some parts rely on the load to have correct voltages.  Check your cathode circuitry. Is seems like your tubes are not pulling a load on the ef86 and E88cc. 

Are you using 2 high voltage power supplies?

Are there any resistors in the heater supply path? Are you testing with only one channel hooked up at a time?  It doesn’t make sense that your heaters could show 4.4 and 6.6 V at the same time
 

iomegaman

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guavatone said:
It’s really not a good idea to test without tubes in because some parts rely on the load to have correct voltages.  Check your cathode circuitry. Is seems like your tubes are not pulling a load on the ef86 and E88cc. 

Are you using 2 high voltage power supplies?

Are there any resistors in the heater supply path? Are you testing with only one channel hooked up at a time?  It doesn’t make sense that your heaters could show 4.4 and 6.6 V at the same time

This is only one channel I've opted to only power one channel at a time at this point until I can get it ironed out...

This is running the DC heater voltage out of your PSU...on the terminals b4 load I get 6.3 across the DC heater

I'm using the Edcor wired exactly as you document for the HT Power three wires twisted to HT power on PCB negative next to ground, 275/275 on other two posts...

My DC heaters go from the PSU to the terminal post on the board nothing in between...

I do have the "power-link" section on the pre-amp PCB populated but not hooked up since I am only running one channel at this point...

 

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iomegaman

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This is the "modified gain setting channel"...thats why resistors are pulled up/missing...using the gain switch also modified according to your newer HF values...

I've disconnected DI/PAD boards until I can sort out voltage values...this preamp has worked in the past but the values were always a little wonky and gain was not huge but I'm using a Jensen JT-13k7 for input and its only 1:5 step up, but clean...Edcor out Tranx..


Resistors at top/left are the newer values, replacing originals and eliminating the VR-1/etc...

 

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guavatone

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All your measurements seem to be referenced from ground to the pin right?

When measuring heaters pins 4 and 5 just measure the voltage between the 2 pins and not to ground. The heater is quite low. And most likely throwing off other operation point voltages.

What do you get between pins 4 and 5?
 

guavatone

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Ok. It appears you still haven’t modified the DC heater supply. Remove regulation parts for heaters as well as the 2 6.8 Ohm resistors.

What diodes are you using for heater regulation? Very very important!
 

iomegaman

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guavatone said:
All your measurements seem to be referenced from ground to the pin right?

When measuring heaters pins 4 and 5 just measure the voltage between the 2 pins and not to ground. The heater is quite low. And most likely throwing off other operation point voltages.

What do you get between pins 4 and 5?

Ah yes, just measured to ground so these numbers are whack...(doh!)

Will modify PSU now and get back to you...
 

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