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Re: Marlboro - Quadra Sound Blender QBS

Posted: 04 Apr 2016, 07:18
by Blitz Krieg
Intripped wrote:Am I wrong if I say that you had better take those two 20n capacitors off?
I mean C1 and C2, aren't they two "death caps"?
Bernardduur wrote:Yep, and already done!

They were also part of the noise in my unit
just remove them and it's already better?

Re: Marlboro - Quadra Sound Blender QBS

Posted: 04 Apr 2016, 15:18
by Bernardduur
Blitz Krieg wrote:
Intripped wrote:Am I wrong if I say that you had better take those two 20n capacitors off?
I mean C1 and C2, aren't they two "death caps"?
Bernardduur wrote:Yep, and already done!

They were also part of the noise in my unit
just remove them and it's already better?
Yep!

Re: Marlboro - Quadra Sound Blender QBS

Posted: 04 Apr 2016, 15:20
by Bernardduur
Mattyr wrote:I've used a qsbII for many years and I love it. Recently my reverb broke and upon inspection I found that the small wires that hold the spring had broken. The wires have what appears to be a small magnet that sits between the two bars connected to the transducer. How can I repair this and where would I get parts, including a new spring as I would like to alter the effect slightly. I have no education in electronics but I'm not stupid so I think with some direction I should be able to do this. Any input would be greatly appreciated.
I have searched for the same reverb but to no avail. You can have mine as I replaced mine with a Accutronics reverb tank (much better reverb now)

Re: Marlboro - Quadra Sound Blender QBS

Posted: 04 May 2016, 18:02
by Mattyr
If you're offering me your qsb reverb tano I enthusiastically accept! Let me know and we can figure out a way for me to pay the shipping fees

Re: Marlboro - Quadra Sound Blender QBS

Posted: 18 May 2016, 09:24
by Bernardduur
Mattyr wrote:If you're offering me your qsb reverb tano I enthusiastically accept! Let me know and we can figure out a way for me to pay the shipping fees
Of course, you have a PB

Re: Marlboro - Quadra Sound Blender QBS

Posted: 13 Jan 2017, 12:25
by abogicevic
Bernardduur wrote:Schematic time:
Preamp.JPG
Reverb.JPG
Tremolo.JPG
Thanks for schematic, really appreciate it :thumbsup

I also have Marlboro G-50R.
It's wonderfull sounding amp, but it's a bit noisy when I turn it on.
Is it problem with old capacitors, maybe amp needs recap? Do you solved that problem with your amp?

Re: Marlboro - Quadra Sound Blender QBS

Posted: 20 Jan 2017, 11:49
by Bernardduur
My amp became a lot more quiet with new caps. I also added a zobel network

Re: Marlboro - Quadra Sound Blender QBS

Posted: 04 Feb 2017, 12:41
by abogicevic
Bernardduur wrote:My amp became a lot more quiet with new caps. I also added a zobel network
Thanks! I'll recap mine too. And, ialso I'm going to change reverb tank.

Re: Marlboro - Quadra Sound Blender QBS

Posted: 22 Apr 2018, 21:05
by pablomago
What reverb tank did you put in your QSB II? I have a few small tanks around.

Re: Marlboro - Quadra Sound Blender QBS

Posted: 31 Jul 2018, 09:51
by Bernardduur
pablomago wrote:What reverb tank did you put in your QSB II? I have a few small tanks around.
I'll check when I'm home!

Re: Marlboro - Quadra Sound Blender QBS

Posted: 12 Aug 2018, 21:18
by Bernardduur
Bernardduur wrote:
pablomago wrote:What reverb tank did you put in your QSB II? I have a few small tanks around.
I'll check when I'm home!
It is a P-RMOD-8AB2A1B

Re: Marlboro - Quadra Sound Blender QBS

Posted: 19 Jan 2020, 03:52
by RingyDaDing
I have the QSB II and it seems to have lost it effects almost completely. Signal is going through ok accept when I click on to the echo setting the volume decreases a fair amount. I have a few questions. Advanced warning I am a novice. 1) Would it be the "Tropical Fish" capacitor I have a close-up of here causing this? It appears to be cracked open. I'm think maybe so. I have some Mullards of the same on the way. 2) I am thinking about replacing the tank, maybe with the one mentioned on here. (Accutronics - P-RMOD-8AB2A1B) If I do this is there anything special I need to do & do I reconnect the same ceramic disc tone capacitors on the exit, if so are they the best for the job? 3) Anything else I can do to improve the unit?

Thanks in advance!

Re: Marlboro - Quadra Sound Blender QBS

Posted: 20 Jan 2020, 11:44
by Zokk
Hello
the general rule with old electronics is to change first all the electrolytics capacitors, so you can have a steady power supply and make measures of the rest of the circuit clearly.
Those "tropical fishes" capacitors are prone to cracking, if you want to avoid further problems I'd suggest to replace it with a modern film capacitor.
Apart from being nice and colored, they are not better for audio than other film capacitors. If you want an upgrade use a paper in oil cap, or styroflex caps... but you probably won't hear any difference in this circuit.

Then if you still don't have any reverb effect, you may want to check the signal patch with an oscilloscope or an audio probe ( http://diy-fever.com/misc/audio-probe/).
I'm not sure about the wiring of the tank, it seems only two pins are connected to the tank, the middle pin seems unconnected and is used as support for the output caps.
Yes you can replace both ceramic cap by film caps.
You need to measure the tank input and output impedance to get a proper replacement tank, it's not just a matter of spring size.

Also this effect creates the "echo" trick by chopping the reverb tail with a square wave tremolo, funny but not really an echo.
With new caps the LFO should have a better shape and you may have less volume drop with this setting.