Yaseu FT-225RD. Counter reads 2 Mc/s low - UK Vintage Radio Repair and Restoration Discussion Forum

OldBlueBear · 11th May 2011, 8:30 pm

Hi, I have my FT225RD since 1982 always worked great. Brought out of storage; the counter reads around 2MHz low but output checked with a counter shows it to be correctly "in band" as per the analog dial. Has anyone seen this fault before or can suggestion a "fix" ? 73s, OBB.

Station X · 11th May 2011, 8:56 pm

I'm not familiar with this rig, but counters in transceivers are generally preset to start counting from some point other than zero. For example on receive with an IF of 10.7 MHz and the LO on the low side the counter will start counting from 10.7 MHz.

Something similar will apply on transmit, for example the counter may start at 9 MHz if a 9 MHz SSB filter is used.

Is the error exactly 2 MHz? If so I expect the counter is not being preset correctly. If the rig covers more than 144 to 146 MHz check the other ranges. It could be something as simple as a dirty wavechange switch.

davidw · 12th May 2011, 7:48 am

This is a 2 metre multimode AM,FM,SSB,CW

Quote:

Originally Posted by Station X

Is the error exactly 2 MHz?

Is the fault the same on all modes? Could it be thinking it's in SSB; the counter will then allow for the offset. Just a thought as I'm also not familiar with it hands on.

Station X · 12th May 2011, 9:48 am

Circuit diagram available free here:-

http://f6csx.free.fr/DOC/FT225RD/FT-225RD_Schematic.pdf

I see that this rig has four bands each 1 MHz wide from 144 to 148 MHz. Is the error the same on all bands, in all modes and in transmit and receive?

Andrew2 · 12th May 2011, 10:07 am

Could this old lady have forgotten where to start counting from because an internal battery has passed away? Unlikely I know, but some older rigs did some strange tricks with battery-backed memories.

frsimen · 12th May 2011, 7:15 pm

OBB

This transceiver uses a simple method to display frequency. The output from the PLL oscillator is mixed with a reference frequency of around 129.3MHz (exact frequency depends on the mode the set is switched to) and the difference frequency of 4 to 6MHz is counted by a simple frequency counter chip. Any offset requirements are obtained by pulling the 129.3MHz oscillator frequency slightly. The 129.3MHz oscillator is derived from a 14.3367MHz crystal passing through two tripler stages.

If your frequency error is constant across the whole band, I would check the operation of the 129.3MHz reference signal. You have a frequency counter, so it should be a simple matter for you to check its output frequency. If the frequency is wrong, check it in all modes, in case one of the diode switches is faulty.

The circuitry involved is described in the full service manual, which is available for free download from the Fox Tango club website.

Paula

11th May 2011, 8:30 pm	#1
OldBlueBear Diode Join Date: May 2011 Location: Mayo, West of Ireland. Posts: 1	Yaseu FT-225RD. Counter reads 2 Mc/s low Hi, I have my FT225RD since 1982 always worked great. Brought out of storage; the counter reads around 2MHz low but output checked with a counter shows it to be correctly "in band" as per the analog dial. Has anyone seen this fault before or can suggestion a "fix" ? 73s, OBB.

11th May 2011, 8:56 pm	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Yaseu FT-225RD. Counter reads 2 Mc/s low I'm not familiar with this rig, but counters in transceivers are generally preset to start counting from some point other than zero. For example on receive with an IF of 10.7 MHz and the LO on the low side the counter will start counting from 10.7 MHz. Something similar will apply on transmit, for example the counter may start at 9 MHz if a 9 MHz SSB filter is used. Is the error exactly 2 MHz? If so I expect the counter is not being preset correctly. If the rig covers more than 144 to 146 MHz check the other ranges. It could be something as simple as a dirty wavechange switch. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

12th May 2011, 9:48 am	#4
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Yaseu FT-225RD. Counter reads 2 Mc/s low Circuit diagram available free here:- http://f6csx.free.fr/DOC/FT225RD/FT-225RD_Schematic.pdf I see that this rig has four bands each 1 MHz wide from 144 to 148 MHz. Is the error the same on all bands, in all modes and in transmit and receive? __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

12th May 2011, 10:07 am	#5
Andrew2 Nonode Join Date: Mar 2010 Location: Dukinfield, Cheshire, UK. Posts: 2,038	Re: Yaseu FT-225RD. Counter reads 2 Mc/s low Could this old lady have forgotten where to start counting from because an internal battery has passed away? Unlikely I know, but some older rigs did some strange tricks with battery-backed memories. __________________ Andy G1HBE.

12th May 2011, 7:15 pm	#6
frsimen Heptode Join Date: Jan 2011 Location: Croydon, London, UK. Posts: 773	Re: Yaseu FT-225RD. Counter reads 2 Mc/s low OBB This transceiver uses a simple method to display frequency. The output from the PLL oscillator is mixed with a reference frequency of around 129.3MHz (exact frequency depends on the mode the set is switched to) and the difference frequency of 4 to 6MHz is counted by a simple frequency counter chip. Any offset requirements are obtained by pulling the 129.3MHz oscillator frequency slightly. The 129.3MHz oscillator is derived from a 14.3367MHz crystal passing through two tripler stages. If your frequency error is constant across the whole band, I would check the operation of the 129.3MHz reference signal. You have a frequency counter, so it should be a simple matter for you to check its output frequency. If the frequency is wrong, check it in all modes, in case one of the diode switches is faulty. The circuitry involved is described in the full service manual, which is available for free download from the Fox Tango club website. Paula