Matchless Tornado Layout

[mebond11]

Greetings,

Attached is a layout (my first) of the Matchless Tornado 15W tremolo amp, for potential perusal by interested members.   Omitted from the layout are the PT, rectifier, filaments, and output transformer circuits.   A couple of modifications to the Tornado schematic:

1.  I used a switch between two coupling cap values on the single preamp stage between .0022 (specified), and .022. Not sure if this will be worth it.

2.  32uf/32uf can cap in place of two .33uf filter caps.

3.  The Tornado schematic for the tremolo was incomplete, so I substituted the trem circuit from the similar Hurricane.   But there were a few differences, I don't know if they are meaningful.   The Tornado has a 2.2K resistor to the grid, omitted in the Hurricane.   One of the RC resistors in the trem loop is a different value.   And, the speed pot is 1M in the Hurricane and .5M in the Tornado.  I believe the higher value means more speed range so that's what I used.

4.  I'm not totally sure I don't have the leads reversed on the trem pots.

5.  The schematic shows a tremolo output capacitor of two .1uf polarized caps back to back...I substituted a .047uf.

The board layout from right to left is the preamp section, tremolo circuit, PI, then output tubes.

I hope I got reasonably close with this...there wasn't much to work with on the web.  Thanks so much for any input anyone wants to provide.  This forum has been an invaluable resource for me.

Link to the Tornado Schematic: 

https://www.thetubestore.com/lib/thetubestore/schematics/Matchless/Matchless-Tornado-Schematic.pdf

The hurricane schematic:

https://www.thetubestore.com/lib/thetubestore/schematics/Matchless/Matchless-Hurricane-Schematic.pdf

[sluckey]

You need to post your layout as a pdf, jpg, etc. Not many diy users here.

[mebond11]

Thank you, my apologies.

[mebond11]

PDF attached

[kagliostro]

Maybe your layout is perfect as is


if was my layout maybe I'll put the cathode resistor and bypass cap (of the power tubes) on the right sight of the PS filter capacitors and move the 32+32uf cap a bit more to the right (as to have shorter connection), but, as I told, maybe your version is perfect as is


Franco

[turtle441]

Also, I'd think about how the power filter cap grounds are connected.  Right now, all nodes are grounded at what I'll call the "power-amp ground" point near the cap can.  While your cathode resistor/bypass cap for the pre-amp tube is going to the "pre-amp ground" by the input jack.  Might want to consider connecting those two electrolytics to the pre-amp ground as I believe it can help minimize ground loops/excess noise.  In my Matchless-style build, I found the easiest way to do that was to shift the electrolytics' placement on the board to closer to the segment of the circuit you were filtering.  It's an easy move, and in your case I think you could end up with one fewer long under-board run.

[mebond11]

Thank you for the input.  I originally had the power tube cathode resistor and bypass cap after the power filters, not sure why I moved it to the end.

[sluckey]

Since the trem is applied to the output tube grids, I suggest grounding the INT and SPEED pots to the power ground.

[mebond11]

Thank you.

[DummyLoad]

100K screen resistors are a problem. move the 22uF supply for the preamp tube V1 closer to the V1 on the board.  split the ground rail from the power tubes - e.g., attach 120R and 220uF to the plate/screen supply ground. 


--pete

[mebond11]

Thanks, what is the issue with the 100K screen resistors, and what does moving the V1 22uf closer to V1 accomplish?

[mebond11]

Also, can you explain what you mean by split the ground rail from the power tubes?   The cathode resistor and bypass cap for the power tubes are grounded with the power rail, if I understand what you are saying.   If I move one of the .22uf caps closer to V1 is it ok to ground that cap to the preamp ground?

[shooter]

here's a pic

as for 100k G2's  they wil basically cut any current, so no control, kinda makes having a G2 useless

[sluckey]

The screen resistors should be 100Ω IAW the schematic. I prefer to put the preamp filter cap near the preamp circuit. Look at this lightning layout...

     http://sluckeyamps.com/lightning/matchless_lightning.pdf

If you don't want to move the preamp filter cap then separate it from the power ground and connect to the preamp ground. See attached pic...

[shooter]

look at my Sluckeys modified layout, see how the caps for the pre amp are away and on a different ground

[mebond11]

Thanks, I put in 100k accidentally in the layout.   Should’ve had my glasses on.  Thanks for the input on the grounding. 

[mebond11]

Thank you for all your invaluable input!

[mebond11]

Hello all, I completed this amp and it was a fun project.   I enjoyed getting the board built, the faceplate fabricated, and fabricating all the chassis cutouts.  Kudos to Doug, who shipped the board one hour after I placed the order. 

To my surprise the amp worked more or less as it should.  I built it according to sluckey’s grounding scheme above...PI filter cap, tremolo filter cap and tremolo controls grounded to the power ground. 

I am having a bit of trouble with the tremolo.  With no input, I get a bit of a quiet thumping above about 6 on the depth pot, and when I move between 9 and ten on the pot I get a pop and the thumping becomes more pronounced right when the pot touches maximum. 

I’m attaching a link to a video taken about 6 inches from the speaker showing the pot in various positions, at around half volume.  I don’t know how close this is to the way it should sound. 

The tremolo itself is strong...in fact too strong above 6 on the pot. 

Also, when the tubes are just warming up, I get a brief rustling sound that disappears when the tubes are warmed up.   

Thank you all for your thoughts on how to tame this tremolo.

[sluckey]

Put a .047µF cap across the outside lugs of the intensity pot. Then put a 47K resistor between the intensity pot wiper and the two 220K resistors. Any better?

The sound you have up to 5 on the knob is normal. Beyond 5 the trem is overdriving. Perfectly matched output tubes may let you turn the intensity up more but I wouldn't bother. The cap should smooth the trem some and the cap and resistor will also cut the trem signal down a bit. It's OK to fine tune the value of the added cap/resistor for your ear.

[mebond11]

Thank you, I will try it and report back.   Thanks for all the continuing help, this community is invaluable!

[mebond11]

Sluckey's changes did the trick...I have to say without this forum I would have dejectedly quit this hobby two years ago.

If I want to pull back the tremolo a little further, I assume the solution is to increase the resistor value?

Out of curiosity, I wonder why this problem developed if I built the same circuit as the old commercial amp...higher modern line voltage or perhaps different aftermarket \power transformer?  I also substituted slightly different cap values than the schematic... .022 uf for the specified .02 and .047 for .05.

[sluckey]

If I want to pull back the tremolo a little further, I assume the solution is to increase the resistor value?

Yes. A larger cap say .1 will help also.

I'm always a little sceptical about hand drawn schematics when I don't know the author. I've always wondered about those back to back .1µFs. Makes no sense at all. That could be a drawing error. The second cap may be connected to ground in the actual amp. That would make more sense.

How does the trem sound with a guitar plugged in? Smooth? Enough intensity for you?

[mebond11]

The trem sounds great, very lush.   It’s a little too much for my tastes at maximum, but I may just leave it.

I read online that back to back polarized caps is a way to make a virtual non-polarized capacitor with a higher voltage rating.   It is a way to save money to get a high value/high voltage capacitor.  But makes no sense in this context, it seems to me.

I agree using an incomplete hand drawn schematic may have been a perilous choice for my first foray into this.

I will probably do another one of these amps and make some layout changes and refine it a little more. 

Thanks again for all the help.  The help I received was the difference between failure and success. 

[sluckey]

Probably good to have a bit more intensity than you need. You'll find that the intensity changes a bit as you vary the speed. That's normal.

[mebond11]

After Sluckey's comment that the back to back .01 uf caps in the hand drawn Tornado and Hurricane schematics didn't make sense (which I had replaced with a single .047), I thought I would look at the Matchless standalone Vibrobox schematic, on the theory that the circuits might be similar.   It looks to me like the Tornado schematic is mistaken...not two .1 uf caps in series, but rather a .1 uf cap followed by a second .1 uf capacitor going to ground.  Sluckey's suggestion of a .047 uf cap between the outside lugs of the depth control is essentially this second cap.   I replaced the two caps with .1's, and it improved the tremolo...the first .1 reduced the max speed by about 25% and made it more musical and less harsh.  I'm attaching the Vibrobox schematic if anyone wants to look at it.
 

[Pietro]

isn.t the tremolo section the same as the one found on the marshall 18 watt? Maybe you can use that as a reference.

Its pretty difficult to build trems when you do this the first time.

[tubeswell]

Re: the trem thumping, you can decrease the maximum intensity by adding a (say 100k to 470k) resistor in series between the coupling cap from the LFO stage and the input lug of the trem depth pot.

[mebond11]

Re: the trem thumping, you can decrease the maximum intensity by adding a (say 100k to 470k) resistor in series between the coupling cap from the LFO stage and the input lug of the trem depth pot.

Thanks, I did do that and it helped tame the tremolo circuit.   The only schematic of this amp online is an incomplete and handdrawn one... the schematic shows back to back .1 uf capacitors, which didn't make a lot of sense....it looks to me like the schematic resource is wrong, that one of the caps goes to ground instead of being in series.   who knows though...there were only 22 of this amp made.

[tubeswell]

...it looks to me like the schematic resource is wrong, that one of the caps goes to ground instead of being in series.

Yep - good guess I'd say - whoever drew the schematic probably reverse-engineered it from looking at an actual amp, and didn't understand what they were looking at. Whereas, the original amp may have been implementing a R/C (low-pass) shelving filter on the LFO output - like the one on the Fender Vibroverb (6G16)

[mebond11]

...it looks to me like the schematic resource is wrong, that one of the caps goes to ground instead of being in series.

Yep - good guess I'd say - whoever drew the schematic probably reverse-engineered it from looking at an actual amp, and didn't understand what they were looking at. Whereas, the original amp may have been implementing a R/C (low-pass) shelving filter on the LFO output - like the one on the Fender Vibroverb (6G16)

I fooled around with different values and came to an arrangement I liked...I posted an updated layout of the arrangement I arrived at.   The amp sounds great, very bright, which I believe is characteristic of Matchless amps.  It's quiet, and the tremolo is on the mellow side but it appeals to me.  It was a fun project that stretched my highly limited capabilities.