LGB F7B with dead sound

[adverse camber]

Help and advice required please.

I have 2 LGB F7B units with dead sound boards. Both are relatively modern DCC versions. I have checked as far as is possible that the fault is in the board and not the power link to it or the speakers.

The obvious solution is to replace the sound board but short of buying a second and B unit and swapping them out these seem impossible to obtain.

Next most obvious solution is to find and appropriate sound only board (or even one for each unit), but I cant find anything that looks remotely suitable let alone one that will run two speakers in the A and B unit.

I have investigated the wiring. The two pin plugs are the power to the B unit which has no pick up of its own. The speaker wires are in 2 of the 4 pins in the 4 pin plug and I have not totally worked out what the other two pins do but suspect it is related to the switch that controls where sound comes from when running an ABA consist.
Also in the B unit are wires from the wheel rotation detector and the two reeds on the dummy motor block that plug into the sound board.

The only thing I can come up with is Massoth and ESU DCC units, the ESU even running 2 speakers. The problem is that if I put this in the A unit I have to throw away a perfectly good control system there and wont be able to use the reed and wheel rotation detectors, while if I put it in the B unit (my preference) there is no motor to plug into the board, and I am under the impression (possibly wrongly) that these units need the motor feedback to work properly and provide the appropriate sounds at the right time.

Has anyone encountered or better still solved this problem? All advice gratefully recieved

Many thanks

AC

 

[PhilP]

As you have wheel sensors, these can tell the decoder the unit is moving.

It seems a bit of a coincidence, that you have two units that aren't working?
It could be you have a faulty lead between the units? - I am assuming you are using the same leads.

I would also try the volume pot, at different positions..
Some are wired backwards, so 'off' when you think they are at full volume, and they don't seem to like being stored in the damp.
Wanging (technical term) the pot, from end to end, can cure this.

PhilP

 

[adverse camber]

Thanks. Have still got a couple of working B units so I swap them to test the leads which are fine. Have tried the volume but with no luck. Will sit them by the aga for a day or two ( with planning permission from the management) But woul be surprised though very happy if that work.

AC

 

[Dan]

Sound goes through the 4 wire cable, 2 wire cable is track power. Switch on rear does select 2 A units or the A/B config. If set to 2 A units and the B unit is hooked to only one A unit and volume control end is at this A unit, you will never get sound. Also never tie 2 b units together with the 4 wire cable, but the 2 wire track power cable is OK. Reason for this is 4 wire cable is the speaker multiplxer.

 

[John Fedak]

Help and advice required please.

I have 2 LGB F7B units with dead sound boards. Both are relatively modern DCC versions. I have checked as far as is possible that the fault is in the board and not the power link to it or the speakers.

The obvious solution is to replace the sound board but short of buying a second and B unit and swapping them out these seem impossible to obtain.

Next most obvious solution is to find and appropriate sound only board (or even one for each unit), but I cant find anything that looks remotely suitable let alone one that will run two speakers in the A and B unit.

I have investigated the wiring. The two pin plugs are the power to the B unit which has no pick up of its own. The speaker wires are in 2 of the 4 pins in the 4 pin plug and I have not totally worked out what the other two pins do but suspect it is related to the switch that controls where sound comes from when running an ABA consist.
Also in the B unit are wires from the wheel rotation detector and the two reeds on the dummy motor block that plug into the sound board.

The only thing I can come up with is Massoth and ESU DCC units, the ESU even running 2 speakers. The problem is that if I put this in the A unit I have to throw away a perfectly good control system there and wont be able to use the reed and wheel rotation detectors, while if I put it in the B unit (my preference) there is no motor to plug into the board, and I am under the impression (possibly wrongly) that these units need the motor feedback to work properly and provide the appropriate sounds at the right time.

Has anyone encountered or better still solved this problem? All advice gratefully recieved

Many thanks

AC

Have you investigated the ESU Loksound 5 FX? It hasn't motor control functions and can be used for its sound functions only. That is what I am considering for use with REVO receivers with no sound.

 

[AlanL]

I faced the same problem a few years back when the sound decoder in my LGB F7B unit died.

I considered fitting a Massoth XLS board to the A unit but that wouldn't provide sound to the B unit. Also the wheel sensor and reed switches wouldn't be connected without a lot of stripping down to fit the relevant parts from the B unit into the A unit.

One option was to use an ESU V5 XL decoder because it had a dual speaker output.

This was my choice and I am very pleased with the operation and sounds of this decoder.

I modified the internal wiring of both units so that the 2 pin connector cable carries the 2nd speaker output to the B unit. I didn't bother about the wheel sensor or reed switches, they remain in the B unit and are not used. The magnet triggered sounds are not important to me but if needed I'm sure that they could be transferred to the A unit.

The sound is amazing and the sound from each speaker is slightly different (to my ears).

In operation, when you throttle up, the loco does not move for a couple of seconds but the sound of the EMD 567 prime mover increases in revs and you then hear the electrical noise (traction motors etc) increase. Finally the loco's start to slowly accelerate. The acceleration on mine is set to a high value (CV 3) and it takes 30 seconds to reach top speed. The maximum top speed (CV5) has been reduced to around half.

When I start the loco, I set the speed to max 28 (steps) and leave it to slowly build speed until it reaches speed step 28. That is a comfortable and realistic speed on my line. It is most pleasing in operation to hear the prime mover gradually increase in revs, and it has the addition of random squealing flanges that sound intermittantly.

The only down side is that the Loco doesn't give a starting warning signal that LGB and Massoth decoders do feature. But having said that I have not delved into the complexities of settings on the ESU decoders and perhaps it may be possible. Apart from changing the address, top speed, mid speed, acceleration deceleration and total volumn the decoder is ex factory.

Highly reccomended

Alan

 

[Greg Elmassian]

You don't need a dual amp to use 2 speakers... most large scale units have plenty of power, and you can either series or parallel a couple of speakers.

 

[PhilP]

You don't need a dual amp to use 2 speakers... most large scale units have plenty of power, and you can either series or parallel a couple of speakers.

But if you series, between two units, and then run one, no sound.
Parallel would be 'better'. - IMHO.

PhilP

 

[Greg Elmassian]

The solution is more complex, since not all locos have lower impedance capability, so I purposefully did not start talking about:

1. series vs parallel
2. 4 ohm vs 8 ohm
3. max power output
4. min amplifier output impedence
5. etc.

All I am saying is you don't need to limit yourself to decoders with dual amps/outputs.

 

[adverse camber]

Many thanks for the comments and suggestions. Keep them coming

AC

 

[adverse camber]

Thanks for the suggestion of the Loksound 5 FX a pair of them one in each car might solve the problem and 2 are still less than an ESU Loksound XL. I had been looking into the same idea with Massoth emotion s but that seems impossible to get in the UK. I will need to check that they can cope with the existing speakers as they look as if they are intended for 00 gauge.

 

[adverse camber]

Thanks again

looked into the Loksound5 FX but they are designed for smaller locos and only output 1w. Keith at coastal DCC said he didn't think they would be able to cope.

BUT just back from the Warwick show where I found a rather bashed up and repainted F7B unit with working sound for half the price of a new sound DCC chip. Now I just need to swap it over into my non working one. I will keep you posted

AC

 

[LGB333]

Thanks again

looked into the Loksound5 FX but they are designed for smaller locos and only output 1w. Keith at coastal DCC said he didn't think they would be able to cope.

BUT just back from the Warwick show where I found a rather bashed up and repainted F7B unit with working sound for half the price of a new sound DCC chip. Now I just need to swap it over into my non working one. I will keep you posted

AC

For DC Analog operation, you can use one of several DC/DCC sound-only decoders: Massoth S with US Diesel Sound Loaded; LGB 65003 American Diesel; and the Phoenix Sound PB17 with US Diesel Sound Loaded (maybe no longer in business). I've never tried using the ESU LokSound 5X and also doubt its specs would support two large 8 ohm speakers.

I've installed sound decoders, both motor/sound and only sound, in several customers' LGB F7A-F7B diesels by placing the decoder in the F7A unit and then run the sound output wires in parallel to the speaker in the F7A and also to the little circuit board with the 2-pin and 4-pin sockets in the rear of the F7A. I first remove the circuit board and then Dremel-out the circuits to the 2-pin connector to isolate it from the existing 2-pin/4-pin circuits, then solder the speaker wires to the back of it and reinstall the board. I do the same on the F7B's 2-pin/4pin circuit board and then solder speaker wires from it to the speaker in the F7B unit while maintaining the proper polarity. Then to connect the sound from the F7A unit to the speaker in the F7B unit, you use the regular 2-wire double plug connecting cable. Takes a little detailed Dremel work, detailed soldering and patience! The newer Marklin-produced LGB F7A - F7B Diesels use this same method to connect the speaker in the F7B unit to the sound output of the F7A's MSD3-mfx/dcc sound decoder.

By the way, I've also used this technique to wire the speakers in LGB F7A-F7B-F7A diesels that I converted to a Massoth XLS DCC Sound Decoder in the lead F7A and Massoth XL Motor Decoder in the rear F7A., which runs the speaker wires through all three units...........takes even more patience!

 

[adverse camber]

Thank you
tought I woul provide an update. I had 2 failed B sound units one old analogue and one newer digital.

I had the good fortune to find an old much kit based B unit at the Warwick show at a reasonable price. The bottom half was intact and the sound working. Swapping out the tops was easy and I now have a working B unit.

The second digital unit I stripped out the old board and replace it with a Locksound XL chip. Expensive but provides sound to both cars. I chose not to mess with the A unit though the chip could have happily run both. I have chosen not to use the sound volume control or the contact Reed’s that trigger the horn and bell. Only really possible if you dig right into the guts of reprogramming the chip, and life is to short for that.