Hi Chaz ? The problem is known to occur with the VOX-UNIT on a >40 year old device. Q604 is only a comparator that switches the relay RL-1 (TX) when pin6 is LOW. ? This can have the following causes: - the ANTI TRIP circuit has no effect on the comparator getting a LOW level on Q604/Pin6.
It is rather the opposite if e.g. C620 (10uF) makes a short circuit. - the VOX AMP circuit is more likely to be a fault candidate. For example, C613 (2.2uF) can leak,
and pull the level to GND via R639 (1k) on Q604/Pin6. - also keep an eye on the transistor Q603 (2SC373). If this has a short circuit C-E,
then the level at Q604/Pin6 is pulled to GND.
? Good luck and best 73 de Roland, HB9GAA ? ? 
?
HB9GAA
Brunnhaldenstrasse 8
3510 Konolfingen
Switzerland
Tel: 41 (0)31 792 04 60
Mail: hb9gaa@... ? ? Hi, all, I see there was some other thread about a vox problem, but no resolution posted. ?I’ve been tracing the schematic and reading the manual and taking measurements, but I’m having an issue that my vox is always on no matter what. ?This came on suddenly, one time I powered on the radio and it went straight into continuous tx and will not exit to rx. ?The big Rl-1 clicks and it goes straight to tx on power up every time. To use the radio, I found that I can disconnect pin 4 of Q604 on the vox card. ?This is the output of the SN 72560 level detector. ?With this disconnected, the radio receives as normal, and transmits on keying the mic. I replaced that Q604 chip, but still have the same problem. This is where I’m getting confused: if I measure the voltage to ground of the blue mic wire (it normally connects to pin 4 of Q604) without Q604 connected, it is at 13.8v on rx and 0v on tx. ?So it would appear that the 604 chip would need to hold that line at 13.8 or similar volts to not close the RL-1 relay and send the unit into tx mode. ?However, the supply voltage to Q604 is only 6 volts. ?So how does a 6 volt supply turn off the relay? ?With that chip connected, the unit goes straight to tx mode, and the voltage on the output of Q604 goes to about 3.5 volts. Monitoring the input to Q604, it drops when I speak in the mic and goes up again when quiet, so the mic side of the vox would seem fine. Wonder if anyone else has had issues like this, or can suggest a possible solution.
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Hi, all, I see there was some other thread about a vox problem, but no resolution posted. ?I’ve been tracing the schematic and reading the manual and taking measurements, but I’m having an issue that my vox is always on no matter what. ?This came on suddenly, one time I powered on the radio and it went straight into continuous tx and will not exit to rx. ?The big Rl-1 clicks and it goes straight to tx on power up every time.
?
To use the radio, I found that I can disconnect pin 4 of Q604 on the vox card. ?This is the output of the SN 72560 level detector. ?With this disconnected, the radio receives as normal, and transmits on keying the mic.
?
I replaced that Q604 chip, but still have the same problem.
?
This is where I’m getting confused: if I measure the voltage to ground of the blue mic wire (it normally connects to pin 4 of Q604) without Q604 connected, it is at 13.8v on rx and 0v on tx. ?So it would appear that the 604 chip would need to hold that line at 13.8 or similar volts to not close the RL-1 relay and send the unit into tx mode. ?However, the supply voltage to Q604 is only 6 volts. ?So how does a 6 volt supply turn off the relay? ?With that chip connected, the unit goes straight to tx mode, and the voltage on the output of Q604 goes to about 3.5 volts.
?
Monitoring the input to Q604, it drops when I speak in the mic and goes up again when quiet, so the mic side of the vox would seem fine.
?
Wonder if anyone else has had issues like this, or can suggest a possible solution.
?
Thanks in advance…
?
Chaz, KC3ZPB
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Re: 10 watt amp finals needed
Thanks !!!? This morning I found one on ebay and if it is a dud, I will get back to you.
Bob..KH2BR
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Re: 10 watt amp finals needed
I’ve probably got some driver boards untested. I have lots of parts, Bob. I’m just about to fire up this 301s ?7 H xxxxxx
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On Jun 18, 2024, at 8:07 AM, Robert Holsti via < kh2br.w6@...> wrote:
Does anyone have or know of a substitute for the 10 watt amp finals ??
the original part number is a s10-12 Rober KH2BR
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10 watt amp finals needed
Does anyone have or know of a substitute for the 10 watt amp finals ??
the original part number is a s10-12
Rober KH2BR
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Re: To Dave Bohlen CW filter.
It is a FT301 analog that needs the amp and is arriving thursday. It may need other things so I better wait so please reserve a 600hz filter for me and the amp if you have one. I could use my Juma amp if not. Here is my direct e$mail and you will have to
remove the ft301 from the start and end plus replace AT with the @ symbol and Dot with a period.
FT301rholstiATicloudDOTcomFt301? here is my p$hone number and the same thing?
remove ft301 from the start and end and remove the @ symbol.? FT3019516@439026FT301.
Thanks and 73's,
Bob KH2BR
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Re: To Dave Bohlen CW filter.
I undestand completly Bob. I have a 600 khz filter as I had mentioned. 25 bucks.. I have also RF decks if you wish to put it on the back of the one you have coming. Make sure it isn’t an SD. SD’s were a stripped down version and were only 10 watts. Those are valuable because you can run a Ukrainian kit ?tranverter off of them easily. They can be upgraded but it is a bit of work. I’d swap you a high power one for it if it’s an “SD”. The SD does not have the plug on the back for the RF deck to plug into. Well it does but is covered by a hard to find SD cover. Good luck on the new one. I wouldn’t buy anything with a serial # earlier than 77 G xxxxxx . ’76 and real early 77’s had the early filter board among other things. Some of them work ok. 77G xxxxxx and on are the best ones.
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On Jun 3, 2024, at 4:36 PM, Robert Holsti via < kh2br.w6@...> wrote:
[Edited Message Follows] I have? radio number one that has only a ssb filter and it is strapped to the AM and CW position. The problem with a ssb filter being used in CW is that strong stations near my operating frequency produce agc action and I have difficulty copying that weak cw station due to agc pumping. Thats why a cw filter is necessary. It? is very noticeable while there is a contest going on. The radio number two has all 3 filters installed but the 250hz cw filter in the cw slot is to narrow. I like it but there are some guys that dont know how to zerobeat be so I dont hear them at all.? I would never use a 250hz filter in AM mode, its to narrow.
The sotabeams filter works like a champ but you still suffer from agc action since it is hooked up to the earphone jack. I have another FT301 arriving this week but it does not have the amplifier on the back
and the insides will be a mystery box with good or bad surprises.? Bob KH2BR ?
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Dave Bohlen
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Re: To Dave Bohlen CW filter.
I have? radio number one that has only a ssb filter and it is strapped to the AM and CW position.
The problem with a ssb filter being used in CW is that strong stations near my operating frequency produce agc action and I have difficulty copying that weak cw station due to agc pumping. Thats why a cw filter is necessary. It? is very noticeable while there is a contest going on.
The radio number two has all 3 filters installed but the 250hz cw filter in the cw slot is to narrow. I like it but there are some guys that dont know how to zerobeat be so I dont hear them at all.?
I would never use a 250hz filter in AM mode, its to narrow.
The sotabeams filter works like a champ but you still suffer from agc action since it is hooked up to the earphone jack.
I have another FT301 arriving this week but it does not have the amplifier on the back
and the insides will be a mystery box with good or bad surprises.?
Bob KH2BR
?
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Re: To Dave Bohlen CW filter.
Not sure I follow Bob. Did you strap the SSB filter to the CW filter slot on the filter board? I actually have a mod to ?select all there filters on the front panel but it’s a lot of work. AM filter 250! Ouch. But CW filters are common 25 bucks. I have plenty. When you select CW do you get IF noise? If it goes dead then all you need to do is strap the SSB filter in. I do enjoy a CW filter but have no problem using SSB filter on CW. 73
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On Jun 3, 2024, at 2:29 PM, Robert Holsti via < kh2br.w6@...> wrote:
I dont know how to send a private message on here, so this is the only way. Dave How much do you want for the 600HZ cw filter?? I discovered that the SSB filter will not cut it in CW mode. Or Do you know how to force the filter I have to increase its band pass ?? Bob KH2BR
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Dave Bohlen
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To Dave Bohlen CW filter.
I dont know how to send a private message on here, so this is the only way.
Dave How much do you want for the 600HZ cw filter?? I discovered that the SSB filter will not cut it in CW mode. Or Do you know how to force the filter I have to increase its band pass ??
Bob KH2BR
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Re: Mode switching problem or normal operation ?
Ok, Here is the symptom. Even with the symptom and it is not a solid fail. The radio works ok even with the symptom.
with no key plugged into the key jack, rotating the mode switch thru all of its positions,
no relays click which is good.
Plug the key into the key jack, starting from the cw position, rotate the mode switch left to the USB position. Result is that the t/r relay clicks. You can hear it and see it.?
I have 2 radios that I swapped the boards out with and the relay still clicks with the cw key plugged into the key jack. That mode switch sure has a lot of wires on it. I am not in a desperate
position with the need to swap it out with my parts rig since the radio works. I dont want to give to much information right now but that may come later. (information over load )
Bob KH2BR
?
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Re: Mode switching problem or normal operation ?
That sounds like a fun problem. I need to hear the symptoms again. I ran into something similar once and it was a problem with the VOX stuff I haven’t worked on one of those in years and the memory isn’t what it used to ?be. Hi I could put a mule on the bench and compare voltage reading with you.
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On Jun 2, 2024, at 7:40 AM, Robert Holsti via < kh2br.w6@...> wrote:
[Edited Message Follows]
Turning the anti trip did not work, swapping out the vox unit board did not help so today I will spend my time tracing wires. Robert KH2BR
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Re: Mode switching problem or normal operation ?
The manual is just better than nothing barely. Hi
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On Jun 2, 2024, at 7:40 AM, Robert Holsti via < kh2br.w6@...> wrote:
[Edited Message Follows]
Turning the anti trip did not work, swapping out the vox unit board did not help so today I will spend my time tracing wires. Robert KH2BR
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Re: Mode switching problem or normal operation ?
600 is to wide.. I have a sotabeams DSP filter here that I will try. It may be better then any mechanical filter. They have trace comparisons between a collins filter and sotabeams. Very impressive difference.. take a look. ? ?
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Re: Mode switching problem or normal operation ?
I warmed up the computer and asked it. Says a 90c is 600hz. If that works for you I have one.
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On Jun 2, 2024, at 7:40 AM, Robert Holsti via < kh2br.w6@...> wrote:
[Edited Message Follows]
Turning the anti trip did not work, swapping out the vox unit board did not help so today I will spend my time tracing wires. Robert KH2BR
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Dave Bohlen
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Re: Looking for a 500 HZ cw filter or workaround
Hi Bob. The 90c is the cw filter for the 301. I’m not finding the spec on that straight away but I think it is 500hz. I have plenty of them and will trade with you. Confirm the band width. 73
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On Jun 2, 2024, at 7:09 AM, Robert Holsti via < kh2br.w6@...> wrote:
I have installed in my radio a 250HZ cw filter, 8999.3 khz? does anyone have a 500HZ filter they would like to sell or trade for the 250 hz filter I have???
Robert KH2BR
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Dave Bohlen
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Looking for a 500 HZ cw filter or workaround
I have installed in my radio a 250HZ cw filter, 8999.3 khz?
does anyone have a 500HZ filter they would like to sell or trade for the 250 hz filter I have???
Robert KH2BR
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Re: Mode switching problem or normal operation ?
Turning the anti trip did not work, swapping out the vox unit board did not help so today I will spend my time tracing wires.
Robert KH2BR
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Re: Mode switching problem or normal operation ?
Make sure the anti trip is up.
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On Jun 1, 2024, at 10:55 AM, Robert Holsti via < kh2br.w6@...> wrote:
[Edited Message Follows] When I switch from CW mode to USB, The t/r relay momentarily energizes and releases and the relay on the blanking unit energizes and de-energizes. When I switch from AM to CW it seems like the t/r? relay energizes and does not release but I can receive ok. when I switch back to AM, the relay de-energizes. Is this normal operation or what should I look for.? FT301D ?
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Re: Mode switching problem or normal operation ?
I soaked the mode switch with Deoxit and that did not fix the problem. I turned the vox gain all the way down and that did not help? BUT !!! ,,,? I discovered what is causing it.
When the? CW key is UNplugged from the radio, the malfunction goes away.
Now, I have some where to start looking.
Thanks for the replies. Robert KH2BR
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Roland HB9GAA