Does anyone know the rated filament voltage for the IFR1500 CRT (V6401)? I am winding the HV transformer from scratch and used the number of turns as specified in the service schematic. For the filament 2 turns are listed and that gives me 5vac. If the filament voltage is greater than 5vac then I can adjust the turns as needed.
Thanks for any help.
Bruno
IFR1500 CRT Filament Voltage
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Re: IFR1500 CRT Filament Voltage
The output voltage may depend slightly on the version CRT controller board. The transformer wasn't changed but the early version used a feedback winding to setup the primary oscillations.
The later version used a fixed frequency chopper daughter board and no longer used the feedback winding. These later versions also added a series resistor to the filament.
From what I recall on the later version the filament output was around 6-8 VAC RMS. ( be careful the filament winding is tied to the high voltage !) but 5 VAC may be correct if it's the earlier board with no series resistor. The service manual has the notes on this.
The 1500CRT high voltage transformer was a poor design due to the 'flying leads" attached internally. The vibrations seems to have caused the leads to wear through to the 200V winding or internally short to the other loops of the high voltage.
The later IFR 1200 CRT transformer is electrically equivalent if you have the later fixed oscillator daughter board on the CRT controller. Used the base from the old transformer and a nylon nut & bolt ( yeas I drilled a hole in the PCB's ) to retrofit.
KG Electronics is still selling the 1200 CRT transformer and that setup does not have the internal connections that can punch through ...that usually took 15+ years to happen though so either way you should be good until the CRT finally dies.
The later version used a fixed frequency chopper daughter board and no longer used the feedback winding. These later versions also added a series resistor to the filament.
From what I recall on the later version the filament output was around 6-8 VAC RMS. ( be careful the filament winding is tied to the high voltage !) but 5 VAC may be correct if it's the earlier board with no series resistor. The service manual has the notes on this.
The 1500CRT high voltage transformer was a poor design due to the 'flying leads" attached internally. The vibrations seems to have caused the leads to wear through to the 200V winding or internally short to the other loops of the high voltage.
The later IFR 1200 CRT transformer is electrically equivalent if you have the later fixed oscillator daughter board on the CRT controller. Used the base from the old transformer and a nylon nut & bolt ( yeas I drilled a hole in the PCB's ) to retrofit.
KG Electronics is still selling the 1200 CRT transformer and that setup does not have the internal connections that can punch through ...that usually took 15+ years to happen though so either way you should be good until the CRT finally dies.
Re: IFR1500 CRT Filament Voltage
jry
Thanks for the info. I have the older version that uses the feedback windings to a relaxation oscillator. No filament resistor and yes, I certainly wished I had the chopper oscillator version - a much better design.
I'll look through the service manual and this time read through slowly to see what the rated filament voltage is. As you know these pot core transformers become problematic. I used Belden Beldsol wire which is rated for 1075 volts so I am hoping I get the distance out of this effort. Rubadue wire has a higher breakdown voltage, but I gave up trying to find an affordable quantity.
To deal with the tendency of the pot core electrical vibration I epoxied each HV layer and used 3M HV acrylic tape. I do have Kapton tabe but the adhesive was not as strong as the acrylic type. Hopefully all will work out in the end.
Thanks for the info. I have the older version that uses the feedback windings to a relaxation oscillator. No filament resistor and yes, I certainly wished I had the chopper oscillator version - a much better design.
I'll look through the service manual and this time read through slowly to see what the rated filament voltage is. As you know these pot core transformers become problematic. I used Belden Beldsol wire which is rated for 1075 volts so I am hoping I get the distance out of this effort. Rubadue wire has a higher breakdown voltage, but I gave up trying to find an affordable quantity.
To deal with the tendency of the pot core electrical vibration I epoxied each HV layer and used 3M HV acrylic tape. I do have Kapton tabe but the adhesive was not as strong as the acrylic type. Hopefully all will work out in the end.
Re: IFR1500 CRT Filament Voltage
Other option would be to add the chopper daughter board and use the off the shelf transformer.
The chopper is only a handful of components and a 1/8 aluminum L bracket for the transistor mounting and heatsink. Using SMT components may be a thought if going this route.
Sounds like you have it either way
The chopper is only a handful of components and a 1/8 aluminum L bracket for the transistor mounting and heatsink. Using SMT components may be a thought if going this route.
Sounds like you have it either way
Re: IFR1500 CRT Filament Voltage
just an update: the new rewind is working great - filament supply at 5vac, B+ at 210vdc and for the HV measuring I used a Tektronix 40Kv probe and 1v setting on the scope so the HV seemed to be around neg 2300vdc. Best of all - no audible transformer hum or buzz. I used epoxy on the windings so it should stay put. Time will tell. Now I have to figure out why its deaf.
Re: IFR1500 CRT Filament Voltage
The poor RX is typically someone keying into the RX port ...probably blew some of the components / attenuators. Not too bad to access since it's on the top shelf .
Usually re-build the fixed attenuators with surface mount resistors of the correct value forthe required 20db --the cans can be opened and re-soldered to repair. You will want to verify the RX port on all three levels - 0,20 and 40.
You may also want to verify the Duplex port as well ...usually get both even though there is a 6db pad inline ...doesn't save the other parts if the power is high enough.
Usually re-build the fixed attenuators with surface mount resistors of the correct value forthe required 20db --the cans can be opened and re-soldered to repair. You will want to verify the RX port on all three levels - 0,20 and 40.
You may also want to verify the Duplex port as well ...usually get both even though there is a 6db pad inline ...doesn't save the other parts if the power is high enough.
Re: IFR1500 CRT Filament Voltage
RE: 1300MHZ IF RX - the 5.6 ohm resistor and a few pin diodes turned into carbon dust. No doubt someone pumped quite a few watts into the Ant port. The MA47047 pin diodes are difficult to find so I used A5S303 pin diodes as a sub. They are basically the same except 100 reverse voltage instead of 200 and 1.5 instead of 3 ohm max resistance. Now I get good signal between the Ant port up to the mixer input, however, with the mixer in the circuit it loads down the signal by 40db so I ordered a new mixer. Also, the 1300MHZ bandpass filter looks like it has an issue. With both ends of the bandpass filter disconnected and with 1300MHZ from a sig gen input at -30dBm I barely see an output. I am not familiar with that type mechanical so I am reluctant to dig into that section.