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The Tube Amp Doctor - Range King power booster
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blackbunny (18 Apr 2018, 11:02), dv8r601 (26 Mar 2018, 20:26), fuzzbunny (27 Mar 2018, 16:31), Intripped (27 Mar 2018, 08:35), karul (27 Mar 2018, 02:47), Manfred (26 Mar 2018, 22:39), modman (28 Mar 2018, 14:00), sixthfloor (28 Mar 2018, 10:32), Zokk (28 Mar 2018, 10:08)

apollomusicservice
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Looks like intestines on the part behind the dpdt switch. Thanks for your degoop work. Very good
dv8r601

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R1 & R2 are both 100k? Is that verified?
Thx.
fuzzbunny

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fuzzbunny wrote:R1 & R2 are both 100k? Is that verified?
Thx.

I ran a simulation of this circuit and found the collector voltages as follows:

Using R2 = 100kOhms : 1.8 Volts DC
Using R2 = 10kOhms: 7.7 Volts DC

A collector voltage of about 7 Volts is common in the known Rangemaster circuits.

IMO the Value of R2 must be 10kOhms.

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dv8r601 (29 Mar 2018, 00:04)
Manfred
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I made an an approximative PCB layout of the analog part for retracing the circuit.

RK_Detail.JPG

The resistor which is labeled with the question mark is marked as R1 in the schematic.
At this point in the shot a resistor with following rings is shown:
yellow - violet - black - ? - braun.
The colour of the fourth ring looks like yellow.
Makes this sense because in this case the resistor would be 4.7 Megohms.

Which is the right colour?

RK_ShotDetail.jpg
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Manfred
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The symbol of the DC jack is wrong in the schematic, sleeve and tip have been mixed up.

JackDetail.jpg
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Manfred
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Manfred wrote:
fuzzbunny wrote:R1 & R2 are both 100k? Is that verified?
Thx.

I ran a simulation of this circuit and found the collector voltages as follows:

Using R2 = 100kOhms : 1.8 Volts DC
Using R2 = 10kOhms: 7.7 Volts DC

A collector voltage of about 7 Volts is common in the known Rangemaster circuits.

IMO the Value of R2 must be 10kOhms.

I did a quick breadboard with Apollo's schematic values but subbed a 10K in the R1 position.
I used a variable resistor in the R3 position ( collector) and biased by ear.
The circuit sounded best with approx. 4.5v on the Collector, R3 around 50k.

The sound was ok but I think something is not quite right with the schematic/details as they are presented. I had a good look at the photos and it doesn't quite add up.

Don't get me wrong, I appreciate the great contributions Apollo makes to the forum! I just wanted to pass,on my findings for others to build on..

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Manfred (15 Apr 2018, 08:58)
fuzzbunny

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I did a quick breadboard with Apollo's schematic values but subbed a 10K in the R1 position.
I used a variable resistor in the R3 position ( collector) and biased by ear.
The circuit sounded best with approx. 4.5v on the Collector, R3 around 50k.

Thanks for your work, I appreciate it very much.
I ran a simulating using with R3 = 50k which confirms your results.
Don't get me wrong, Don't get me wrong, I appreciate the great contributions Apollo makes to the forum! I just wanted to pass,on my findings for others to build on..! I just wanted to pass,on my findings for others to build on..

I think, to pass findings is one of the most important things here.
I appreciate the great contributions Apollo makes to the forum too.
Manfred
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Manfred wrote:The symbol of the DC jack is wrong in the schematic, sleeve and tip have been mixed up.

JackDetail.jpg

There is nothing wrong with DC jack in my schematic

apollomusicservice
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In the Specifications of the TAD Rangeking you can find;
- jack for external 9VDC power supply (tip: ground, sleeve: 9VDC)

In your schematic the sleeve is connected to ground and the tip to +9VDC

RK_DC_jack.jpg
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Manfred
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In the Specifications of the TAD Rangeking you can find;
- jack for external 9VDC power supply (tip: ground, sleeve: 9VDC)

In your schematic the sleeve is connected to ground and the tip to +9VDC

RK_DC_jack.jpg

Still I don't understand, in my schematic Tip (or Pin) is on the ground.
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apollomusicservice
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Sorry, now I understand, you using an another drawing symbol for the DC-jack like I do, then the schematic is of course correct.

I use this drawing symbol, that was the point of confusion for me.
DC-Jack-Symbol.JPG
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Manfred
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I bought a Rangeking for a very favourable price yesterday.
I measured the passive components and some voltages too.
For a proper measure of R2 it was necessary to interrupt the conductor after its lead,
because I want not degoop the PCB.
I found:
R1 = 470 Kiloohms
R2 = 2.2 Megaohms
The calculation with the read values gives a DC-gain of about 430 for the transitor.

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Manfred
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From looking at the photos, R1 looks like 4M7 to me (yellow-violet-black-yellow-brown) but i could be wrong.
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rs wrote:From looking at the photos, R1 looks like 4M7 to me (yellow-violet-black-yellow-brown) but i could be wrong.

Indeed, I measured R1 with 470k an R2 with 2M2.
I ran a simulation with the new values which confirm the read voltage values.

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rs (20 Apr 2018, 17:00)
Manfred
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I ran the simulation with a BC548C transistor because a BC550C is not available, but both Types have nearly the same values.
Here a shot of the simulation.

RKS.jpg
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rs (20 Apr 2018, 17:01)
Manfred
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Manfred wrote:
rs wrote:From looking at the photos, R1 looks like 4M7 to me (yellow-violet-black-yellow-brown) but i could be wrong.

Indeed, I measured R1 with 470k an R2 with 2M2.
I ran a simulation with the new values which confirm the read voltage values.

Thanks Manfred but here is another one photo, R2 is still questionable. Unfortunately, the pedal is no longer with me.
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apollomusicservice
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Thanks, for the another photo, I would say that the fourth ring is orange.
Manfred
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