Tram Titan 2A

[gary68]

I am looking for a vfo or a 31.700 oscillating crystal.

Is the vfo stable enough for use above channel 23?

[2600]

To move the receiver dial up 30 channels, this would start channel 1 on the dial at channel 26. Since the dial's original coverage stops at channel 23, this is the better choice. Since the factory receiver crystal is 31.5 MHz, this calls for a 31.8 crystal, not 31.7 like a Browning receiver.

We found that a crystal marked 10.595 MHz will work just as well. The reeiver's oscillator circuit will triple the crystal's frequency no problem.

At least with the one we tried. The 10.595 MHz might be easier to track down already made. Ken's electronics lists this one for 12 bucks.

www.kenselectronics.com/lists/cbxtal.htm

Getting a crystal custom made gets more expensive all the time.

The transmit VFO is a different challenge. The drive level coming out of it has to be really high. And the VFO must be keyed on while transmitting, and off while receiving. Since each transmit crystal operates on your receive frequency, the VFO would put a constant 'spot' carrier into the receiver if it were not put on standby while receiving.

There was a "Tram Diamond 10" VFO sold 40 years ago. It has a shielded wire that connects in place of one transmit crystal, and a second unshielded wire that connects to the mike jack (I think) to key it while transmitting. A knob on the front of the slider provides your spot carrier, not the red button on the front of the radio.

But the Diamond 10 VFO was sold in different versions, and some of them are not compatible with this radio.

The same VFO was also sold with the Maco name on it, also in multiple versions.

Identifying the right one probably requires powering it up, watching the output with a 'scope and counter, while grounding the yellow wire to see if that will key it.

Not an easy item to find.

73

[gary69]

Nov 19, 2018 16:13:36 GMT -5 gary68 said:

I am looking for a vfo or a 31.800 crystal.

Is the vfo stable enough for use above channel 23?

[gary69]

Nov 21, 2018 0:43:48 GMT -5 2600 said:

To move the receiver dial up 30 channels, this would start channel 1 on the dial at channel 26. Since the dial's original coverage stops at channel 23, this is the better choice. Since the factory receiver crystal is 31.5 MHz, this calls for a 31.8 crystal, not 31.7 like a Browning receiver.

We found that a crystal marked 10.595 MHz will work just as well. The reeiver's oscillator circuit will triple the crystal's frequency no problem.

At least with the one we tried. The 10.595 MHz might be easier to track down already made. Ken's electronics lists this one for 12 bucks.

www.kenselectronics.com/lists/cbxtal.htm

Getting a crystal custom made gets more expensive all the time.

The transmit VFO is a different challenge. The drive level coming out of it has to be really high. And the VFO must be keyed on while transmitting, and off while receiving. Since each transmit crystal operates on your receive frequency, the VFO would put a constant 'spot' carrier into the receiver if it were not put on standby while receiving.

There was a "Tram Diamond 10" VFO sold 40 years ago. It has a shielded wire that connects in place of one transmit crystal, and a second unshielded wire that connects to the mike jack (I think) to key it while transmitting. A knob on the front of the slider provides your spot carrier, not the red button on the front of the radio.

But the Diamond 10 VFO was sold in different versions, and some of them are not compatible with this radio.

The same VFO was also sold with the Maco name on it, also in multiple versions.

Identifying the right one probably requires powering it up, watching the output with a 'scope and counter, while grounding the yellow wire to see if that will key it.

Not an easy item to find.

73

what crystal does the 10,595 replace?

[2600]

The crystal you're looking for is in a socket on the main chassis away from all the transmit crystals, alongside V2. In the manual, it's shown as "X2". The frequency of this one is marked 31.5 MHz.

The tricky part is to unhook one side of this crystal so you can switch the new one in it's place.

Running long wires from this crystal to a switch on the front or rear can disrupt the oscillator circuit, and prevent the crystal from running reliably.

Using a small relay placed next to the crystal socket would keep those wires short, and the long wire to the upper-band switch would be controlling only the DC power to the relay coil.

But you'll have to also build a rectifier circuit to borrow 6.3 Volts AC from the heater supply so you'll have DC voltage to power the relay coil. A 6-Volt DC relay is the simplest to use, since you need only one rectifier diode and small filter cap to power the coil.

The radio doesn't have any available voltages from the stock power supply to do this.

There's usually nothing simple about modifying a 50 year-old radio.

I attached a pdf file of the manual for this radio. Figure 4 and figure 5 show the location of the crystal X2.

73

Attachments:

Tram Titan II 23 Channel CB.pdf (736.87 KB)

[gary69]

Is the schematics for the Tram Titan II the same as the IIA?
Does the 10.595 give transmit and receive?

[2600]

Let's back up a step here. This is not like newer 23-channel radios that control both transmit and receiver from one set of shared crystals.

It's more like a Browning. A separate transmitter and receiver, but both in the same cabinet. The only parts of the radio that get shared between transmit and receive side are the audio and the power supply. The same tube that drives the receiver speaker also modulates the transmitter.

But those 23 crystals control only the transmit frequency. The receiver is controlled only by the tuning dial, or a "fix" crystal socket that is empty unless you obtain a custom single-channel receive crystal to plug into it.

The crystal X2 that I mentioned is located away from all the other crystals, because it controls the receive band you cover with the tuneable dial. The stock 31.5 MHz crystal points the dial to channels 1 to 23. To make the channel 1 mark on the dial line up with channel 26 (the next one above channel 23) you need a crystal that is 300 kHz higher than the factory-stock 31.5. That's where the 31.8 MHz comes from.

The only reason that the 10.595 MHz crystal worked is that the oscillator circuit that X2 plugs into selects and amplifies the third harmonic of the crystal. Three times 10.595 MHz is not exactly 31.8 MHz, but it was very close in the radio we tried this. Your mileage may vary. A crystal marked 10.600 would be closer in theory, but only if you can find one. 

And if you buy this crystal and it won't work for you the way it did for us, this is the only way you'll find out.

But at least you'll have to go to a lot of trouble to find out.

Or you could just pull the crystal from the X2 socket and haywire the new crystal into the socket, long enough to try it. If that crystal won't do the job, you didn't waste the expense and effort of building a way to switch between two crystals in the X2 socket.

Don't know if you have ever modified a factory-stock car or truck engine. If so, you'll understand there are some basic skills required.

This thing is old enough that this kind of mod might not be a good 'beginner' project.

But there is no guaranteed "plug and play" solution to make the radio receive more channels.

And expanding the transmit coverage is a separate issue, requiring a separate solution, like a new crystal for each transmit channel, or a slider that matches the quirky requirements of this model.

The tuneable receive dial is the best way to separate radios that use the same crystals to transmit and receive from the ones that don't.

A radio that will cover both transmit and receive together with a single slider hookup almost never has a tuneable receiver dial.

Radios that do have one almost always require two solutions for added coverage. One for receive and one for transmit, like the Titan 2.

Far as I know, the schematic for your radio is nearly identical to the older Titan 2 model. The manual for that one is not posted online anywhere I could find it. Close enough for the frequency-expansion details.

One last thought: All the electrolytic capacitors in this radio are well beyond their original use-by dates. If they still work, that's fine. Just expect them to "remember" how old they are and begin to fail once the radio is put back into any regular service. If you have read advice online to "re-cap" a radio this old, that's what they mean. Every electrolytic capacitor in this radio is a failure risk at the (nearly) 50-year mark. Replacing them all is the only way to make a radio this old reliable at all. 

73