Voltage Measurement of Whistle Control

There has to be a load on the transformer for the D.C. offset to be generated. The greater the load, the larger the offset.
It's not clear to me whether your meters will detect it.
There are tables in the test bench sections of the service manual for acceptable values. The test benches put a specific load on the transformer under test.

With the meters set to AC you should not read any DC voltage. 5 volt compensating voltage seems a tad high. I suspect with an engine on the tracks you would see a lower increase. Different transformers will have a different level of compensation. I think a 1033 is only 3-4 volts more.

Pete

Thanks for the advice.  I haven't taken any voltage measurements with a load.  All I know is my locos take off like a rocket when the whistle button is pushed.  It sounds like the RW is doing a lot of compensating!  I've got a LW on the way.  It will be an interesting comparison.

The reason that the design called for a compensating voltage to be added is that original whistle motors drew quite a bit of current, causing the train to slow down. If you are using the whistle control on newer electronic locomotives, the extra voltage will not be needed by the whistle circuitry and will cause the train to speed up.

On the RW transformer the compensating voltage is 5.4 VAC if the input voltage is 115 VAC. Based on your meter readings, your transformer is doing exactly what it is supposed to.  If you are running more modern equipment, which do not need the extra voltage to power the whistle motor, there are whistle and bell controllers which are added in line with the older transformers that do not add the compensating voltage.  You could start looking for one of these. 

Thanks Arthur and David.  It sounds like the RW is just what's needed for my 6466WX tender.  For my modern stuff, I'll stick to the 6-5906 sound activation button.  Does any one know if the No. 167 whistle controller adds a compensating voltage?  It's got a nice look when running prewar tinplate.

The #167 has a choke to drop the voltage slightly during normal operation so when you activate the whistle you get a boost in power when the choke is taken out of the circuit.  It may not be as extreme as a PW transformer, only way to know is to try it.

I think a 1033 is only 3-4 volts more.

The Lionel Service manual indicates the compensation winding is 5 volts on a 1033.
5.7 volts on an LW and 5 volts on a ZW.
Until today I was under the impression that they were all 5 volts.
I did not check for any other transformer models.

Well, I’ve received the LW I bought off eBay and have taken some measurements.  First I want to explain two things: (1) I’m in Australia with 240V power, so the LW was fed via a step-down transformer, and (2) line voltage can vary at different times of the day according to peak loads etc.  At the time of the test, the LW was being fed with 122V – perhaps a little on the high side?

At a range of different track voltages (without a load) the whistle button generated an additional 5.8V.  So that's matches the specification.

My voltage here is 125-128 almost all the time, other than light bulbs that have a short life, no other difficulties.

Gents, I replaced the selenium rectifiers in my new "old" ZW transformer. It now blows air whistles and activates electronic whistles in the first position. The second position does not produce any sound and blew my initial diode when I held it full on. What am I doing wrong. Is there a remedy? If the second position is no longer needed, can it be bypassed and the first position be routed to both positions? Many thanks

The second position just cuts on a resistor that allows some of the current to bypass the rectifier and reduce the load on it. There is a mixed opinion as to whether the resistor is needed if the diode is properly sized. I am of the opinion it is not. You need to take a hard look inside your transformer and be sure all the wires are going where they are supposed to.  It sounds like the resistor wire maybe contacting something it should not be. Look at the wiring diagram in the service manual.  I think you will find ZW diagrams on this site.

If you have a 15A diode, the resistor shouldn't be needed.  I'm guessing the diode that burned up was much smaller.

John, thanks for your reply. I've ordered two 1,000V 40 amp stud diodes for installation.

If I replace the 2 ohm wire with a straight wire will that up the voltage when the whistle control is placed in the full position? I'm assuming it needs to be about 14 gauge. Currently the 275 ZW shows no DC output with the whistle control fully engaged. I'm taking that measurement with the top on to limit mechanical travel. Many thanks, Tom

Straight wire won't do it, it won't allow any offset voltage.  The resistor divides the current but still allows the diode to impart some DC offset to keep the whistle blowing.  You need some resistance there to allow the DC offset.  I'd find a 1 ohm 20W resistor for the replacement if the stock long wire resistor isn't up to the task.  Here's a suitable candidate: RES 1.00 OHM 20W 5% RADIAL.

I'll order them. Just verifying that replacing the 2 ohm nichrome wire with a 20 watt 1 ohm should improve the likelihood that the whistle will continue to blow in the 2nd position. I'm still confused a bit why it doesn't continue to blow. I will do this after I install the 40 amp 1,000 volt stud diodes.

PS - the diode that blew up was a 10A10 diode (10 amp, 1,000 volt diode). The temporary replacement is holding but I'm avoiding the whistle in the second position.

This is how my ZW year s wired in the event the prior owner’s service guy moved something. Position 2 provides no DC

The nichrome wire is the stock resistor, replace that with the resistor I specified.

Thal,  in your drawing there is a wire missing.  The terminal you show coming from the control arm and orange wire is disconnected when you move the whistle control lever.  The power from the control arm then goes through the orange wire, out to the 5 volt boost winding and should come back to where the diode and resistance wire come together. That boost power goes through the diode and then to terminal D.  In the far whistle control lever position the resistance wire is put on parallel with the diode. If the missing wire is really there, everything should work as designed, even if the resistance wire is open,  unless there is a problem with the whistle control switch.  

Wow David, many thanks. I don’t find the missing wire

I’ve attached a new pdf with the connection terminals marked A-E.

Would you mind replying with a simple point to point connection needed using the newly marked terminals?

I want to avoid an error on my part if possible. Many thanks

Tom

Was

Look at the Lionel diagram of the ZW about 6 posts up.  What you have marked as the orange wire is wire #2 on the Lionel diagram.  What appears to be missing is wire #19.  On your diagram wire #19 should come in at point E, then through the diode to point B. The whistle switch connects B and A together and the boosted rectified power goes from point A to binding post D on the transformer.   You have to look carefully as Lionel’s manufacturing engineers were masters at reducing parts counts. The wire may use some unrelated looking bracket as part of the circuit.  I do not have a ZW apart right now so I can not look myself.

Thanks for your help. I'm putting the ZW aside for now. I can't reliability locate the missing wire. I do believe the prior owner or his service tech had perhaps modified the unit. I'm contemplating using silicon sealer to attach small blocks to restrict the whistle control from going to the 2nd whistle position.

Another member suggested I replace the 2 ohm wire resistor with a 1 ohm 25 watt resistor. I've ordered these but am unsure this will solve the issue as it might be some time of miss wiring or a  worn switch problem.

As I only run trains at Christmas and they are mostly early RailSound Lionel and Protosound MTH trains bought in the late 90s and early 2000s, I'm really out of date with what people use today as far as transformers to run these older engines. Recommendations are welcome. I'm not a year round hobbyist but do appreciate the trains at Christmas. This all started with me wanting to expand beyond 2 tracks.