The Dahl transformer is stock. He supplied them for Ameritron back then. That's an MFJ part number on the tag. If you look at the date on the transformer's tag, it's from 2002. The same as the caps. So the amp is 21 years old. Still should be able to get any parts you need.
The previous owner cared enough to invest in a Peter Dahl transformer and the rest of the power supply, so with good tubes that thing will rock! You can make your own parasitic choke, just wind five turns of solid wire around a resistor that's the same value as the other two. Parasitic chokes are normally mounted as close to the plate connection as possible to reduce the possibility of the lead wire acting like an antenna. If you get the third tube working you should consider upgrading the "doorknob" capacitors as they're a known failure point.
I could make my own and I also have maybe 5 different parasitics that would work laying around already, but I want to have the exact same as the other 2.
@@tramdr I understand your desire to keep it as close to OEM as possible, but sometimes you just have to improvise. I sent you a copy of the manual with the parts list and schematics so maybe that will help.
Tram Dr... Can build this entire amp with eyes closed,he is trying to put it back to as original as he possibly can ..he wants the parasitic chokes to match the others,also because the circuit needs to be identical in this part of the filement and hv network... Be beat if it was the identical same choke... I meen he could pull the 3rd tube out and remove the secondary fil transformer and remove the nice peter daul ..as well and go all back stock .but I don't see this happening....lol that pf transformer gonna be hard to beat, infact if he gets the 3rd tube fired I Wana see the amp load and hv load on this amp ...I bet it is gonna pound out the RMS
MFJ owns Ameritron and should have all the parts you need.The PeterDahl XFRMR is not stock and that transistor I believe not stock.Appears to be moded in a number of places by a cobbler.I would put back to stock and get rid of that xtra tube and that too small of a filament xfrmr on the back.Nice find.
I looked on the MFJ site and they sell a very limited selection of parts. Parasitic chokes was not on their list that I could find. Hence, if anyone has a link or something, send it to me.
@@tramdr If it is a positive keying voltage look up Mr Carson lab repair and modification of TL922 he gives a circuit of a solid state keying diagram using a single transistor placed between the rig and amp no need for a foot switch. Regarding the parrasitic choke I would use a 47ohm 5watt carbon resistor and wind over it about five turns of 18swg tinned copper wire. No need to find the same already fitted in the amp .
I don't believe that circuit will maintain .the filement voltage u need seems way to small of a transformer .. the transistor I believe is used to control the bias voltage regulation..and may show a short when switched to ground..or cut off..the transistor my go open when the voltage is switched at HP
still working on it, but since it goes to the center tap of both the filament transformers, that maybe why its showing a short....or very low ohm readings.
@tramdr nice I knew the amertrons came from the smp supply/ Denton camp. my lk550 has a 1.75ccs amp transformer in it for 3 tubes. bug ok PD filliment transformer to
MFJ Ameritron should have the parasitic choke you are looking for and they are not over priced. Also the Pink bleeder resistors should be replaced, they are notorious for failing. 73 Joe
That external filament transformer is connected to the additional third tube only. It is also rated for one tube only, 5v 15a. The factory internal filament transformer that runs the two factory tubes is under the cap board/metering area pretty well hidden underneath.
I did some tracing and the transistor is used as a divider. One side sends half the bias voltage to the center tap of the original filament transformer and the other side of the transistor sends the other half of the bias voltage to the center tap of the added 3rd tube filament transformer. I do not like this arrangement. I am going to go a different route. The amp originally ran the bias straight off the zener diodes. It used one zener for SSB/high side at 7.5 volts and it switched in the 2nd 7.5 zener in series for a total of 15v's bias on the CW/low side.
Looks like you are right since the output goes to the center tap of the filament transformer. Here is a question that I am not sure of the answer to yet. The non factory transistor is connected so that it isolates the bias from the 2 filament transformers. I'm thinking this is because the bias can't be connected to the center tap of both transformers in parallel. Not sure yet though.
That one really peaks my interest !
The Dahl transformer is stock. He supplied them for Ameritron back then. That's an MFJ part number on the tag. If you look at the date on the transformer's tag, it's from 2002. The same as the caps. So the amp is 21 years old. Still should be able to get any parts you need.
I was going to say that on my next vid on this when I get it going. Good one.
The previous owner cared enough to invest in a Peter Dahl transformer and the rest of the power supply, so with good tubes that thing will rock!
You can make your own parasitic choke, just wind five turns of solid wire around a resistor that's the same value as the other two. Parasitic chokes are normally mounted as close to the plate connection as possible to reduce the possibility of the lead wire acting like an antenna.
If you get the third tube working you should consider upgrading the "doorknob" capacitors as they're a known failure point.
I could make my own and I also have maybe 5 different parasitics that would work laying around already, but I want to have the exact same as the other 2.
@@tramdr I understand your desire to keep it as close to OEM as possible, but sometimes you just have to improvise. I sent you a copy of the manual with the parts list and schematics so maybe that will help.
Tram Dr... Can build this entire amp with eyes closed,he is trying to put it back to as original as he possibly can ..he wants the parasitic chokes to match the others,also because the circuit needs to be identical in this part of the filement and hv network... Be beat if it was the identical same choke... I meen he could pull the 3rd tube out and remove the secondary fil transformer and remove the nice peter daul ..as well and go all back stock
.but I don't see this happening....lol that pf transformer gonna be hard to beat, infact if he gets the 3rd tube fired I Wana see the amp load and hv load on this amp ...I bet it is gonna pound out the RMS
@@justinruth9729Download the manual and read it...even with two tubes the specs are impressive. The trick is in how you tune the amp up.
MFJ owns Ameritron and should have all the parts you need.The PeterDahl XFRMR is not stock and that transistor I believe not stock.Appears to be moded in a number of places by a cobbler.I would put back to stock and get rid of that xtra tube and that too small of a filament xfrmr on the back.Nice find.
I looked on the MFJ site and they sell a very limited selection of parts. Parasitic chokes was not on their list that I could find. Hence, if anyone has a link or something, send it to me.
The Peter Dahl is most likely stock.
Older production models came from factory with Peter Dahl transformers
what would cause the band switch tap from the tank to get hot?
Band switch switches dirty and/or loose so not getting a good connection, and mistuning.
Will that key up with the radio...or do you have to use a foot key up?
foot switch.
@@tramdr If it is a positive keying voltage look up Mr Carson lab repair and modification of TL922 he gives a circuit of a solid state keying diagram
using a single transistor placed between the rig and amp no need for a foot switch.
Regarding the parrasitic choke I would use a 47ohm 5watt carbon resistor and wind over it about five turns of 18swg tinned copper wire.
No need to find the same already fitted in the amp .
I don't believe that circuit will maintain .the filement voltage u need seems way to small of a transformer .. the transistor I believe is used to control the bias voltage regulation..and may show a short when switched to ground..or cut off..the transistor my go open when the voltage is switched at HP
still working on it, but since it goes to the center tap of both the filament transformers, that maybe why its showing a short....or very low ohm readings.
I'll do some searching for the parasitic.
Thanks
do they use a full wave bridge in the ameritrons?
yes
@tramdr nice I knew the amertrons came from the smp supply/ Denton camp. my lk550 has a 1.75ccs amp transformer in it for 3 tubes. bug ok PD filliment transformer to
MFJ Ameritron should have the parasitic choke you are looking for and they are not over priced. Also the Pink bleeder resistors should be replaced, they are notorious for failing. 73 Joe
I couldn't find them there.
Kilgore's electronics near ft. worth Texas might just be able to help you out on the parts...or on info as well...
Thanks
I personally don't think that filement transformer is big enough ..hot me.concerned..
That external filament transformer is connected to the additional third tube only. It is also rated for one tube only, 5v 15a. The factory internal filament transformer that runs the two factory tubes is under the cap board/metering area pretty well hidden underneath.
So in your opinion what do you think the transistor is doing in this circuit
I did some tracing and the transistor is used as a divider. One side sends half the bias voltage to the center tap of the original filament transformer and the other side of the transistor sends the other half of the bias voltage to the center tap of the added 3rd tube filament transformer. I do not like this arrangement. I am going to go a different route. The amp originally ran the bias straight off the zener diodes. It used one zener for SSB/high side at 7.5 volts and it switched in the 2nd 7.5 zener in series for a total of 15v's bias on the CW/low side.
It's going to show a short in line ...
Looks like you are right since the output goes to the center tap of the filament transformer. Here is a question that I am not sure of the answer to yet. The non factory transistor is connected so that it isolates the bias from the 2 filament transformers. I'm thinking this is because the bias can't be connected to the center tap of both transformers in parallel. Not sure yet though.