Questions about the Harvey Wells Bandmaster

[n0tjl]

Hello W4BFS,
Wired it up per your instruction and powered it up. Grid read 1.2ma, plate read 100ma at resonance and output power read 10w. Had the CFC set at 3525kc, the HW set to 20meters and picked the signal up at 14100 on the r390a. The signal sounds ok, maybe not 599 but usable. Now on to rebuilding the HP-23 ps. Can you tell me how to do that? I might get on t am yet.
Thanks and regards,
Tom N0TJL

[w4bfs]

ok Tom....sounds like progress .... need a bit more grid current .... have you tried 80 and 40 meters yet ?
will need some relays for the hp23 .... one to turn on the hv and another to step start it as well as the ptt function ... lotsa different ways to do this ... I would avoid using 120 vac for the coils and use a lower voltage ...this is just personal preference

[n0tjl]

I tried 15M yesterday - almost no grid current at all. I will try 80 and 40 today. My B & W tr switch seems to work also. I bought it at a hamfest years ago in Atlanta.
Tom

[n0tjl]

I checked 80 and 40 today. 80 showed a grid current of 3ma and a plate current of 100ma. Power was 10w. I reduced the grid current to 2ma and both plate current and output power remained the same. 40 showed a grid current of 0.8ma, plate current of 115ma and output power of 7w.
Regards,
Tom N0TJL

[n0tjl]

Does someone have a procedure to convert the Heath HP23B from voltage doubler to full wave bridge rectified? Don't want to dive into that ps without some sound advice backing me up.
Regards,
Tom N0TJL

[w4bfs]

Tom .... I think you are on the cusp of doing great things so have a little faith in yourself and go ....  

to prevent any sort of damage due to error, limit the power to the supply with a series resistor (aka incadescent light bulb) in the 120V ac supply ....notice that when you energize the supply without a load you will see a dull glow in a 100W bulb ...this is normal .... as a quick test intentionally short one of the windings (apply proper safety rules) and note that the bulb comes up to full brilliance but nothing should smoke or pop or other disgusting things .... this is a ballasted test and is recommended for non-destructive testing of new equipment aotbe

[n0tjl]

Sounds like the light bulb variac that I use when I recap old receivers. Start at 25w and go up to 100w bulb with an old receiver that hasn't been switched on in many years. It can save one from a smoky outcome. Is there a schematic that will show me what the ps should look like?
Tom

[w4bfs]

I'm not sure that I understand yer question .... I would be looking at the ac supply for the HW and the Heath ps23 and how to add the necessary relays and such

[n0tjl]

The HW APS-50 ps schematic shows a relay with the coil (battery powered) across pins 7 & 8 and the relay contacts across pins 5 & 6 which connect to the primary windings of the power transformer. My HW xmtr has a battery powered relay installed in it. I assumed that was added later in this xmtr's career when someone else used a nonHW ps and required a relay to operate ptt. The coil of this relay (operating voltage unknown) is wired to a connector on the rear of the xmtr. I vaguely remember reading about an xmtr modification like this but nothing specific was mentioned about the power supply used. That is where I get lost.
Tom

[w4bfs]

ok .... to focus on the added ptt relay ... look at its coil and the movable armature that is mechanically coupled to the contacts .... where the armature is attracted to the pole of the coil, is there a copper ring ? ... this is an indication of an ac coil if present and if absent, a dc coil ... if dc its probably fairly low voltage and a dc supply can help determine this .... if it has the copper (shading) ring you can use a variac to start low and see where it pulls in .... how many contact sets are available ?

[n0tjl]

I don't see a copper ring. Probably dc and has two sets of contacts. The manual discusses installing a 6v relay and that is probably what one of the previous owners did. Could I use a full wave bridge rectifier to convert the Heath HP23B? The rectifier is rated at 1000V, 8A or would that cause problems? The HW APS50 power supply schematic calls for a 12MFD 600v smoothing capacitor and a 25k 20w bleeder resistor in the high voltage output (425v 275ma). Would something like that work in the converted HP23B?
Regards,
Tom

[w4bfs]

1.  I don't see a copper ring. Probably dc and has two sets of contacts. The manual discusses installing a 6v relay and that is probably what one of the previous owners did.
2.  Could I use a full wave bridge rectifier to convert the Heath HP23B? The rectifier is rated at 1000V, 8A or would that cause problems?
3.  The HW APS50 power supply schematic calls for a 12MFD 600v smoothing capacitor and a 25k 20w bleeder resistor in the high voltage output (425v 275ma). Would something like that work in the converted HP23B?
Regards,
Tom

sorry ....I've been busy with family stuff

1.  do you have a variable dc supply ?   if so disconnect one side of the relay coil or verify that it goes to the mic ptt switch .... the idea is to isolate the relay coil so that it is the only load ....bring up the voltage slowly and the relay should activate .... note what the voltage is and what current is drawn

2.  yes the full wave bridge capacitor input will yield 300 - 350V ... 1kV piv is a little low but should be ok .... use an appropriate mov or capacitor to snub spikes .... are there any filter chokes ?  they will eat you up on piv

3.  that was because they used filter chokes .... chokes require a critical minimum current to provide voltage regulation .... use a pi section hv filter with a series resistance of 50 ohms or so, 40uf or greater caps will get the ripple removal job done ....look at the Heath DX60 power supply for ideas

[n0tjl]

Thank you. I have had family visiting over the last two weeks. Granddaughter really wore me out. Fun though. Looks like a wire is disconnected going to the mike connector. Will check it against the schematic then test the relay voltage. I do have a variable dc ps. Can I duplicate the component values in the DX60 ps?
N0TJL

[w4bfs]

Can I duplicate the component values in the DX60 ps?
N0TJL

I suppose so ....  the question is not easy to answer because the dx60 is a tapped doubler and your modified hp23 is now a full wave bridge but the components should work since parameters are similar ... when in doubt, Ohm's law is your friend