Dale Manquen headed to New Jersey

Dale:

 

I'm sure many of us would like to know your progress on your booster amp for the TMCC / Legacy signal.

 

Regards,

GNNPNUT

Ahhhhh...I see you're a "tube guy" Dale. Back when I could still hear pretty good, I exclusively used tube audio amps and preamps. Nothing in solid state comes close to capturing the soul of music like tubes. I just moved to NJ but I actually be in Florida then stupidvising the movers to bring our stuff up here.

Dale we would absolutely love to have you stop by our layout  Let me know what day you want to stop by   I hope that amplifier works for Lyle and us   I have too many TMCC engines.  I will email you my cell phone number

Dale,

 

Is this at all similar to the unit designed by Jim Lefevre?  We at the NJ-HiRailers have been collecting the parts and are just about ready to start construction.    I'd love to see how your unit works on our layout.   

 

I attached Jim's schematic and our parts list. 

 

 

 

 

Where's Heathkit when you need them?

 

Gerry

The last electronics project I undertook was a Heathkit auto dwell/tach meter about 30 years ago.  It actually worked when I finished.  I hope this amp also works when we're finished.

My unit is based upon Jim's design, but adds:

Variable tuning

Variable drive level

Output level monitoring

Sounds good.  What do you think the chances are you will be ready to test the unit at the club?  We would absolutely love to test it.  I have a couple of engines at the club right now that won't hold the TMCC signal reliably.  SD80Macs from the Motor City Express set.

Sounds like a nice rig Dale, it'll be interesting to see how it does at the NJ-HR layout.  That's certainly the "acid test". for boosting the signal!

Just my 2 cents Dale, but if you could test your new TMCC booster at the NJHR club layout you will find the perfect test bench for it. They did alot to get the signal to maximum but there are still some weak spots.

I ran my engine on it and it worked but not like it dose at home. The layout is so big and dynamic that you run into issues that you just don't normally find in the average train room.

 

Good luck and please keep us posted. 

Dale M

 

Just curious,what tubes you are using and why instead of transistors. 5U4,12AX7,6L6,6V6? etc

 

Dale H

2 of the tubes used by Jim Lefevre are a6AQ5 and a 6X4.

Jim D

I have replaced the 6X4 with silicon diodes.  The 6AQ5 is a beam power tube similar to a 6V6, but with a 7-pin miniature base.

Hi Dale H, maybe I can add a little to answer your question. Vacuum tubes always had one big advantage over solid state and that is VT's low noise production and fast response time.

SS has P-N junctions that take time to react thus creating distortion. True the components we have today are much improved over what we had in the seventies but they still not as clean. Smaller, cheaper and lower in power consumption but not as true as VT.

 

In fact a number of years ago I read an article in Scientific American about a guy who was working on microscopic Vacuum Tubes to be used in high speed computers. I never heard anything about his work after that so I have no idea how successful he was.

 

I'm sure Dale M can provide a more detailed description of what he is working on but the above description is in the ball park.  

Another thing about vacuum tubes is they're a lot more "robust" when you abuse them electrically, semiconductors tend to smoke on the spot for large overloads.

Thanks for the replies. I used to rebuild amplifiers for jukeboxes. I have one out now I am repairing.  I understand that high end amplifiers still use tubes and their is some controversy over the advantages. My brother just sent his away to be reworked. High grade 12AX7 tubes (not the Russian ones) are used. A lot of tubes are getting hard to get NOS as well as can type capacitors. I have to put axial ones under the chassis.  The numbers I cited are commonly used along with 6X4s, 6sn7, 6sl7 6J7 etc. OA2 and 2D21 tubes were used for switching circuits,later 2050. 

 

I was always tempted to replace the 5U4 and 6X4 with 1000 volt rectifiers but not sure if it was the right thing to do.

 

Dale H

TMCC at the NJHR layout has gotten pretty bad.  Forget trying to run MUs.  One engine is sure to drop out and start dragging.  Not good.  A friend of mine tried to run his Centipedes at Trainstock .  They have a VERY tiny antenna on the top and they wouldn't run more than 20 feet without dropping. 

 

I've been reduced to running my MTH engines (fire away Ben and Vinny!)

 

We're moving ahead with building Jim F's amp (which Dale says he based his on).  I'm just waiting on one more part. 

 

It will be great to see if Dale's unit helps.  That will give us a lot more confidence that our build will help also. 

 

Keeping our fingers crossed.  Wish us luck everyone!

"TMCC at the NJHR layout has gotten pretty bad. "

 

When was it good?  It actually has gotten better in the past few months

I had that same thought with a Collins Radio power supply. Guys were replacing the 5R4 and maybe also the 5U4 with solid state diodes and using resistors to reduce the voltage somewhat...maybe the surge on turn-on as well.

I was thinking the tubes did all that well. So I didn't replace them and even reconverted one 516F-2 supply that I bought used.
In Dale's case, going solid state makes sense to me...starting out from scratch on the design somewhat and not requiring workarounds to simulate a vacuum tube rectifier.

I guess I'm thinking back to TS 4 when my BSA ES44AC ran and ran with no issues.  Last time I tried it ran OK but not perfect (after I fixed the broken antenna wire). 

The B+ voltage in the booster circuit is low compared to the max rating of the tube.  The extra voltage due to lower drop across the silicon diodes is not very significant.

Some folks like rectifier tubes because they delay the B+ on the tubes somewhat so that their filaments can warm up before the B+ hits, allowing the tube to wake up in the properly biased state.

 

I started out designing a solid state amp, but quite frankly I got lazy.  I thought that Jim's circuit would allow me to determine just what problems I need to address.

 

Last night I did some testing.  I only have 3 TMCC engines - a converted PW F3, a modern F3, and a converted scale brass GG-1.  I have two troublesome areas on the layout for TMCC signals.  One is a PW bascule bridge that stalls the GG-1, especially if the engine is moving very slowly.  When the engine is fully inside the bridge, the signal drops out.  (Yeah, I know - add a earth-ground reference wire....)

 

With my adjustable output control I am able to vary the drive from an indicated value of 0 to 8.  My F3s would run out in the open space with a value as low as .1, but when the GG-1 was stuck in the bridge, not even an 8 would get it out.  I have more to learn here!

 

An op amp driving discrete medium-size transistors was my first idea.  Running on +/- 15V rails, I should get about 30V peak-to-peak output.  Compared to the Base's output of 5V P-P, that would boost the signal by about 15 dB, which should be a healthy boost.

Dale, if you're missing the earth ground side, isn't boosting the track signal going to result in further swamping that weak signal?

The amp is also pumping extra drive into the earth-ground circuit.  What goes in one end of the output coil/transformer from the ground also goes out the other end of the coil to the track.  I would have thought that the gradient between the two components would be increased, but it is apparently not increased enough.

 

BTW, the two pantographs on the GG-1 are the TMCC antenna, and they are in the down-and-locked position to clear overhead obstacles.

Makes sense Dale, I was wondering if you had returned the drive to earth ground.

 

The pantographs on my GG-1's usually work pretty well as antennas, they're a lot better than the little thing that Lionel puts in many of the locomotives.

With a brass shell, I need to have something that is on the outside!

Here is how the trip is shaping up:

I depart L.A. Wednesday 5/22 and arrive late at Newark.

I will be working and staying with an audio customer Thursday 5/23 and maybe Friday 5/23.

My schedule is open Saturday and Sunday, and whatever part of Friday we don't need.

My return flight is Monday morning.

 

My top priority for trains is testing my track signal booster at the NJ Highrailers.  Other than that, I am open to suggestions.  I do have a couple of invites.

Dale, do you have a phone number to contact us at NJHR to let us know when you are coming? if not, let me know and I will email you some numbers.

Please send me the numbers.

Dale

I sent my cell number to you last week

 

Ben

I sent numbers for Ben, Jim D and myself.

I did some more testing with the Booster.

 

First, I decided to work on the GG-1.  I had coupler "tack" that was dragging and shorting out on the center rail joint where the bascule bridge meets the fixed track.  This caused the engine to stall and trip the circuit breaker.

 

While I was fixing that, I decided to swap the Railsounds power supply board that didn't have a shield can for one that did.  Mike Reagan had said that this was a way to reduce the "noise" from the switching power supply that can desensitize the R2LC receiver.  (See my new post elsewhere on making shield cans.)

 

While I was at it, I installed a length of insulated piano wire inside the bascule bridge running from one end to the other down the center on the underside of the top metalwork.  I had a long wire attached to this, but I never connected the wire to earth ground.  This rod could probably still act as a ground signal radiator, which means I may have contaminated my experiment by changing too may variables at once.

 

When I returned the GG-1 to the layout, I did indeed have much better reception.  The bascule bridge still was the worst spot on the layout, but now I could raise the booster's drive level a small amount above minimum and get flawless performance.

 

My other test zone had been where the GG-1 passed under some overhead layout wiring. With the shielded board there were no problems at very low signal levels.

 

I am talking about signal levels that read a couple tenths of a volt on my meter, compared to the full booster output of over 6 volts.  It is really interesting to be able to dial the track signal strength up and down!

 

I have received samples of some higher-frequency medium power transistors (Ft=30 MHz) and I have a high-frequency opamp capable of 50 mA at one MHz on the way.  Running a bipolar 15V supply should give me about as much voltage as the tube booster, but I think it may be more sensitive to output loading, although the opamp is supposed to be able to drive capacitive loads without problems.  Film at 11.....

I fly to New Jersey tomorrow 5/22.

 

My last modification to the amplifier was adding a .1uF/600V capacitor in series at the output.  I wanted some protection for the output coil just in case somebody has a stray voltage between earth ground and the outer rail.

I also changed the knob on the output tuning capacitor for one that has the locking screw deeply embedded into the knob.  My first knob had the screw almost flush with the outer surface.  Guess what - the shaft of the tuning capacitor is at high voltage, and that means the screw is also at high voltage!  Simultaneously touching the knob's screw and ground is an invigorating experience!

Hey guys, try to have some nice weather for me for the rest of the week.

Well, tomorrow we have some very nice thunderstorms and the possibility of a tornado watch, will that do?

 

On the bright side, the rest of the weekend looks to be very nice.

Slow warm up with GZ-34s in my Dynakit MK IV amps are definitely a good idea.  Instead of getting a blast of juice using a SS replacement for the rectifier tube when the amps are turned, they get a gradual B+ warm up that's kinder to the 7199 and EL-34 tubes.

NOS tubes are worth searching out - they typically outlast anything currently in production.

Interim report:

I visited the NJ Highrailers last Friday night.  We tried hooking up my track signal booster.  The open circuit voltage of the booster is 21 volts on the built-in signal strength meter.  With the large layout connected, the output dropped to 1 volt!  There was not a significant improvement on the troublesome loop that we used for testing.

 

If I had used my brain, I would have made the signal strength meter available to also read external voltages so that I could compare the amount of drive directly from the Legacy Base to the layout with the booster's output.  Doh!!!

 

When I get a chance, I am going to load the output down with capacitance to see how much capacitance it takes to drop the output to 1 volt.  I am also going to determine the output impedance of the amplifier.

 

The good news is that I had a great time visiting the Highrailers' layout and also spending a day with Bob Taylor.

 

When I planned the trip, I completely forgot about the Memorial Day weekend.  I probably would have chosen another time.

 

I will write a more complete report after I have researched the output impedance problem.

One wonders if you simply have excessive capacitance with the huge size of the layout.

 

Too bad you couldn't split the layout up and have more than one booster supplying the signal.

I am beginning to suspect that we have something to learn about how and where we run earth-ground wires.  Bundling them with the track power wires may create excessive capacitance and may contribute heavily to the signal drop.

 

I am also wondering about the idea of using coax to run the track signal around.  I don't think coax does much in the way of looking like its characteristic impedance when it is only 1% of a wavelength long.  I need to learn about that. Maybe it just looks like 20 pF per foot of extra capacitance.

I agree, I don't believe the earth ground wires should be bundled, I think they should be separated.  I actually tried to convince other club members of that when we built our modules, but they weren't buying.  We'll see if we live to regret that decision.

 

Well, the track signal has to be on the track, so the coax doesn't seem to bring anything to the party, but maybe I'm misunderstanding how you want to use it.