Vintage Fender Blender Sounds Extremely Gated On All Settings

[antonis]

I plan on getting an atlas dca75 soon. Is that good enough or were you referring to another kind of measuring device?

I think it's a professional-like semiconductor analyzer.. Don't know your needs but it seems like overkill to me for DIY effects build/repair.. Better buy a good DMM and learn how to test semiconductors..  

If you were fixing this issue with the resistors how would you go about doing it?                 

I'd try lowering 10k Collector resistor value..
(8k2 should work..)

Also, the 100k resistor on the base of Q4 is measuring at 67k when I take the battery out. Not sure if something else in the circuit is causing it to read that way.

Take 2 measurements across that resistor by swapping meter probes..
If the one with RED probe on upper leg (the one connected to +9V) is correct, I'd like you to justify it..!!

[antonis]

Just an assistantship on what is happening in regard to Q4 bias..



For your circuit, R1 should be 100k..
Could you guess the value of R2..??

[BrainDrain]

I plan on getting an atlas dca75 soon. Is that good enough or were you referring to another kind of measuring device?

I think it's a professional-like semiconductor analyzer.. Don't know your needs but it seems like overkill to me for DIY effects build/repair.. Better buy a good DMM and learn how to test semiconductors..  

I have a few dmm already but they're just cheap ones. I just wanted one that measures HFE a bit more accurately and the dca55 and dca75 are the ones I always see electronics guys using and recommending. It's something I'll use everyday since I'm constantly building or tinkering so for me it's a good investment.  The cheap ones I have seem to  measure HFE on silicon transistors decent but I don't trust it  for germaniums and the dca meters show the leakage or at least get numbers that are close from what I've read.

Also, the 100k resistor on the base of Q4 is measuring at 67k when I take the battery out. Not sure if something else in the circuit is causing it to read that way.

Take 2 measurements across that resistor by swapping meter probes..
If the one with RED probe on upper leg (the one connected to +9V) is correct, I'd like you to justify it..!!


[/quote]

I thought with resistance it doesn't matter which side each probe is on?  I did it both ways and it's exactly the same each time. It's supposed to be 100k but reading 67k. 33k seems like a pretty decent amount to be off by.

[antonis]

I thought with resistance it doesn't matter which side each probe is on?

You thought right but only when there isn't any diode connected across the resistor..

[Rob Strand]

I plan on getting an atlas dca75 soon. Is that good enough or were you referring to another kind of measuring device?

IMHO, you don't need a semiconductor tester.   Most problems can be evaluated with a multimeter on ohms or diode range.

If you want to measure transistors (BJTs), something like RG's tester is easy to make,

http://www.geofex.com/Article_Folders/ffselect.htm

You can do NPN and PNP also silicon.   It's accurate enough.  The digital units are no better - for that you need a careful set-up which is beyond most DIY'ers needs.

For JFETs,

https://runoffgroove.com/fetzervalve.html

[BrainDrain]

I thought with resistance it doesn't matter which side each probe is on?

You thought right but only when there isn't any diode connected across the resistor..

Yeah that's what I was thinking in regards to other components affecting the reading. Thanks for taking the time to draw it out like that so my brain can understand it better 

So I tried what you said. I wrapped a 47k resistor around the 10k resistor (on the collector of Q4) so the two are in parallel and now equal around 8k2 and the little bit of gating is gone. The notes sustain better too. I'm thinking of adding a 10k trimmer in place of that 10k resistor to fine tune it. Or would it be better to just add an 8k2 resistor and put the bias trimmer in a different spot?

[antonis]

I'd say put the 10k trimmer in place of 10k Collector resistor, trim it according to your taste, take it out, measure its resistance and place the nearest value availiable resistor in place of Collector resistor..
(tripots are not indicated for  set-and-forget enduring use..)

[aron]

I'm trying to remember but the original I thought did gate at times. 
For years it was my worst distortion pedal of all time!
The funny part is that I have come across 2 originals from the 70's in my life. I got rid of the first (and shouldn't have), then someone gifted me a second. But it's in a box and not readily available or else I would chime in.

I guess what I am saying is that it's not a smooth pedal by any means.

[BrainDrain]

I'm trying to remember but the original I thought did gate at times.
For years it was my worst distortion pedal of all time!
The funny part is that I have come across 2 originals from the 70's in my life. I got rid of the first (and shouldn't have), then someone gifted me a second. But it's in a box and not readily available or else I would chime in.

I guess what I am saying is that it's not a smooth pedal by any means.

That seems to be the overall opinion I read almost everywhere. That it's somewhat of a harsh sounding pedal. I was mostly just listening to demos of other ones on YouTube and none of them sounded like what mine was doing so I figured something was a bit off. Sounds a little better now with the slight adjustment thanks to Antonis.  Thanks for chiming in   

[antonis]

That it's somewhat of a harsh sounding pedal.

You can always lift up one leg of Q3 Emitter diode to have a nice bluesy distortion pedal..