Does anyone have these?? I can't find them anywhere.? You'd think some CBer would be selling them on Ebay, but no...

Hello,

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• /Booster AMP Variants.docx

Uploaded By: Randy W7CPA <randybest@...>

Description:
Later model FT-301D units had a relay added to the 100 watt amp not shown on many schematics.

Cheers,
The Groups.io Team

This was my biggest 301 challenge to date.
Glad it's behind me, what a pain, too many rabbit holes!
The unmodified drift is 300-400Hz I'm told, like other rigs from its day.
My KWM2-A drifts that much then settles down.
Having <20Hz drift in 2 hours from dead cold makes this worth the effort.

Cheers

Great!? ? SUPER CONGRATULATIONS !!? Very nice accomplishment and what a wonderful adventure.? Thanks so much for sharing.

Guess I am fortunate that mine is still 100% stock- except I replaced all the electrolytic capacitors a few years back which fixed a couple of pesky issues that had crept in.? Plus I know I replaced that triac fixing the blinking S meter back when it was fairly new.? Fortunately when I first bought it in 1978 I purchased some extra TIL 106's and 108's for the display and still have a few.? Mine drifts about 250 Hz at first turn on after which it is very stable.? I have babied the rig all these years keeping it like new.

I do have the newer display and was going to install it but I decided to keep is as an ace in the hole just in case.??

KEEP THOSE 301'S RUNNING!

More progress on pretty, pretty, keeper final updates.

1. I ordered and assembled the Elcon EL-31 display replacement. I calibrated the display using a precision freq counter and sig gen on the bench. This is easy, just apply 5vdc and have it it. After the simple install all is well, beautiful modern 7 segment displays. I bought 6 spares from Mouser, cheap $1.80.

2. I ordered and assembled the Elcon EL-33 VFO stabilizer. After the somewhat difficult install I was hoping for the most excellent? <20Hz drift in 2 hours like my first FT-301D. Of course, something is wrong with this one >120Hz drift and it never stabilizes. This had a major rabbit hole chase to find the root cause. After considerable debug effort here is what I found:

a. The EL-31 is not drifting and is performing perfectly.
b. The EL-33 is performing as designed to stabilize the VFO frequency. The fake news is coming from the display system.
c. The front panel CALIB pot voltage is what is drifting causing my fake news.This voltage is developed from the reg 5v and controls a varactor diode in the Counter board to vary the display indicated frequency.
5. I changed the 8v and 5v 3 legged regulators to modern TI linear parts to improve reg 5v. This made reg 5v perfect BUT IS NOT THE STINKING ROOT CAUSE of the display drift.
6. The D2211 varactor tuning diode in the Counter Mix card is hyper temperature sensitive. I could blow on it and and it changed the load. I found 10 original NEC parts in TAIWAN and I uploaded the data sheet to Files. My first FT-301D is super stable so this is just a bad part problem.

Hopefully the end is near, I plan some minor calibration touch ups then putting covers on.

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This is what I'm leaning towards, and barring the availability of anything more than rudimentary test equipment would be the easiest to try. If replacement of D1301 doesn't solve the problem then the fault is with Q1301.

73 - Fred, N8YX

I recall having this problem many years ago, kind of fuzzy, but as I recall I simply replaced the triac and all was good again.? That would be easy to try.? Good luck.? It is very nice to see this group helping one another.? ?73

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Steve,

My deep experience is only in the following FT-301D areas so I have no no input for you.

1. 100 watt booster
2. Elcon EL-31 display mod
3. Elcon EL-33 VFO mod
4. IF and Filter board.

The LPF board is a signal purity for FCC compliance, period.
The unfiltered RF has many 2rd, 3rd order harmonics.
The LPF whacks them down.

My blanking and 10 watt amps have always been functional so I haven't had to understand them, sorry.

Best wishes,

Randy

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Yes, there is no continuity between K1 and K2 when the power is on.

I think I'm misunderstanding something. From what I can see on the block diagram, the LPF unit is like a gateway between the PA and then antenna. The relay on the LPF unit needs to be closed in order to transmit. For some reason on this radio the relay is open, which is the root of the problem. I thought by bypassing the relay and just jumping K1 to K2 it would essentially take the LPF unit out of the mix and the radio would transmit. This doesn't seem to be the case. So I think I'm misunderstanding what the LPF and blanking units do.

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I just tried something that I think might change where the fault might be. Maybe I'm wrong about this, but the reed relay is connecting K1 and K2 if I understand things. I decided to risk it and to just jumper k1 and k2 power it on to see if that would hijack the protection circuit (albeit in a potentially harmful way) and get rid of the blinking S-meter light problem. As it turns out, the radio behaves exactly the same way with K1 and K2 jumpered together, bypassing the relay entirely. I'm not the best at reading schematics so I'm not sure if there might be more to it than that, but at the very least this rules out the relay.

Is there something I'm missing, or does this indicate that maybe the problem is with the blanking unite itself and not with pb1445?

Is there something that would cause the protection circuit to trigger as part of a normal behavior (working as intended) even though it’s not transmitting, or is it designed to only trigger in transmit mode? I read somewhere in the manual that the rig would have to be powered down to reset the protection circuit if it was triggered. I’m assuming that means there is something that resets after the power is taken out of the circuit (something that maybe isn’t resetting?) Could that be the problem??

If the the next step is to test Q1301 and D1301, then that’s what I have to do. I would just like to avoid having to desolder these old components if I can. I’m not sure that I have the capability to properly test them even if I get them out without damaging them. Let me know if there are other things you think I ought to test first, otherwise wish me luck and I’ll dive in and give it a shot.

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Looks like Fred's response didnt show up for some reason but it went to my email so i'll post it here:

"Look at the emitter of Q1301 - top of the relay coil. See any voltage there when the rig is powered up?

Thanks for the info, just did as you suggested and it looks like the relay is wide open, no continuity. But does that mean the relay is bad or that it's not being told to activate? Is there a way to apply voltage directly to the relay to test if it is functioning or should I go straight to testing the D1301? Not to get ahead of myself but I'm not sure how I would go about testing the thyristor. I have a cheap chinese "transistor tester" that sometimes can't figure out older components but sometimes autodetects and correctly identifies resisters, caps, diodes, transistors, etc so I could try to use that. I also have a voltmeter/ohmmeter and a cheap chinese oscilloscope that I built from a kit but havent really used yet. I've been doing simple repairs to electronics for many years but I'm just now starting to learn about things more complex than just replacing obviously blown caps and broken wires etc.

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OK, it was actually easier than I thought. Now that I have access to the rear of this board, is there an easy way to test the relay? I feel like testing the relay will be way easier than testing the thyristor?with my knowledge level and equipment, but I'm here to learn.

That's what I was afraid of. This is the one board they don't give you easy access to. I don't suppose there is a trick to accessing the back of this...

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