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Success ?!!!! ? I put the scope on both the working bitx40 and the low power radiuno again tonight. ?Made comparisons. The bitx runs 7 watts and the radiuno would only do 1 w into a 50 ohm dummy load. ?Both radios had a 1004 Hz tone injected at the mic. ?on the scope the AC signal was good up to the 2 diodes d-15 d-16. on the bitx. On the radiuno Farhan has replaced the two diodes with a single dual diode . ?AC signal level look good going into both sides of the dual diode. ?But coming out the dual diode, signal level was very very low and distorted. (all this time the receiver did seem to be receiving but not sure how well) I removed the dual diode and with a fluke DVM measured the front to back on each side. They were identical at 20 M ohms and 80K ohms. ?So it appears that the dual diode tested ok with the meter. ?I did not have any high speed diodes so I took 2 silicon diodes (typical voltage rectifiers) and soldered them in to replace the dual diode. The receiver came up and now the transmitter is putting out 5 watts. ? ? So changing these diodes cured the low 1 watt problem. Now I need to order a diode replacement. ?Not sure I want to use the same diode number. ?As I said this one checks good on dvm but does not work. ?I may just order two seperate 1n4148s like the original board and install them. ? ?Farhan said that the new dual diode was pretty much matched on both sides so he took out the balance pot . ?So maybe i would put in a balance pot and the old original diode replacements.? Are many people having this low power problem that have the radiuno with the dual surface mount diode? Tom ?W5KUB We will be announcing this breakthrough on our weekly ham show Amateur Radio Roundtable at 8 PMCT on Tues night. ?Also if anyone from this group would like to be on the show and talk about the bitx we would love to have you.?
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Tom
Outstanding. I would just leave the dual diode out and make it like your other radio.
Did you notice that you had carrier without the mic plugged in? I have seen a couple of postings about having carrier without the mic.
Keep up the good work and reporting your findings.
Randy, K7AGE
On Wed, Feb 8, 2017 at 6:39 PM, tcmedlin1 via Groups.Io <tcmedlin1@...> wrote: Success ?!!!! ? I put the scope on both the working bitx40 and the low power radiuno again tonight.? Made comparisons. The bitx runs 7 watts and the radiuno would only do 1 w into a 50 ohm dummy load.? Both radios had a 1004 Hz tone injected at the mic. ?on the scope the AC signal was good up to the 2 diodes d-15 d-16. on the bitx. On the radiuno Farhan has replaced the two diodes with a single dual diode .? AC signal level look good going into both sides of the dual diode.? But coming out the dual diode, signal level was very very low and distorted. (all this time the receiver did seem to be receiving but not sure how well) I removed the dual diode and with a fluke DVM measured the front to back on each side. They were identical at 20 M ohms and 80K ohms.? So it appears that the dual diode tested ok with the meter.? I did not have any high speed diodes so I took 2 silicon diodes (typical voltage rectifiers) and soldered them in to replace the dual diode. The receiver came up and now the transmitter is putting out 5 watts. ? ? So changing these diodes cured the low 1 watt problem. Now I need to order a diode replacement.? Not sure I want to use the same diode number.? As I said this one checks good on dvm but does not work.? I may just order two seperate 1n4148s like the original board and install them. ? ?Farhan said that the new dual diode was pretty much matched on both sides so he took out the balance pot .? So maybe i would put in a balance pot and the old original diode replacements.? Are many people having this low power problem that have the radiuno with the dual surface mount diode? Tom ?W5KUB We will be announcing this breakthrough on our weekly ham show Amateur Radio Roundtable at 8 PMCT on Tues night.? Also if anyone from this group would like to be on the show and talk about the bitx we would love to have you.?
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Would be good to figure out a way to check for this fault without unsoldering the dual diode. ?Ohmmeter readings won't quite do it. ?
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Simple, just disconnect the T4 leads to the diodes and then test with a
diode tester on multimeter!
Raj
At 09/02/2017, you wrote:
toggle quoted message
Show quoted text
Would be good to figure out a
way to check for this fault without unsoldering the dual diode.?
Ohmmeter readings won't quite do it.??
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Diode tests good with fluke DVM out of the circuit but it would not function correctly in circuit. Replacing the diodes corrected the problem.?
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I assume there's a scrap of wire across what was the balancing pot at R106. ?Could remove that wire to leave one end of both diodes dangling. ?Then measure forward and reverse current through each diode from a 5v source through a series resistor. ?If we knew the signal level at R39 while transmitting 7W, ?would tell us the appropriate value for the resistor to match that current. ?Unlike using ohmmeters of various construction, this should give consistent readings. Could be the dual diode got partially damaged by heat when soldered in place, giving it a too-high a forward resistance. ?Would be interesting to compare a reading taken using a scheme like the above method on the damaged diode vs a good one. Jerry, KE7ER
On Wed, Feb 8, 2017 at 08:07 pm, Jerry Gaffke wrote: Would be good to figure out a way to check for this fault without unsoldering the dual diode. ?Ohmmeter readings won't quite do it. ? ?
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No. ?Most of the current through the diodes is coming from the BFO, and since that is mostly balanced it doesn't show up at R39. ?I have no idea what that current would be, but possible it's too high for the poor little diode pair. ?And could be we need the 100 ohm balancing pot (or a couple 50 ohm resistors) just to tame that current.
On Wed, Feb 8, 2017 at 09:02 pm, Jerry Gaffke wrote:
?If we knew the signal level at R39 while transmitting 7W, ?would tell us the appropriate value for the resistor to match that current. ?
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This problem has made me and my equipment look pretty bad. I am not sure changing out the PA was a real fix. All I know is, it's not performing like it has enough power. Whether it is low audio drive from the mic, damaged PA, or this dual diode thing. And it seems like a lot of people are having the same weak problem. I've only heard of analog Bitx 40 owners making contacts. If the VFO holds still long enough. I'd like to know more before I cut or remove anything. On my board I have a 3 pin smd part labeled D-20,?IL440. It looks like I would have to solder through hole diodes to the 3 D-20 smd pads. Or to the D-15, D-16 pads and some jumpers across the balance pot, and I think the D-20 pads too. I don't want to go out and look again. I have a strip of 1N4148 diodes. Would I have to check them for matched forward voltage drop? A perfect pair? I got two cheap DMM's and a?12864 Mega328 component tester. Anything else I should know?
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Are you sure the forward resistance is 80KΩ? In that case it's way way out and the diode is no good and it is no wonder that you were not getting enough output. Just for info, before writing this I took a bunch of 1N4148's from a bag that I had bought cheaply from ebay and checked them with a DVM on the diode test position. The forward reading is around 950 and no back resistance reading as they are silicon diodes. Someone else inanother comment said that the diode is marked IL440 which according to Vishay?consists of a GaAs infrared emitter optically coupled to a silicon planar triac chip with a non-zero crossing network.
I am sure that Farhan can clear this up
On Thu, Feb 9, 2017 at 4:03 AM, Randy Hall <listk7age@...> wrote: Tom
Outstanding. I would just leave the dual diode out and make it like your other radio.
Did you notice that you had carrier without the mic plugged in? I have seen a couple of postings about having carrier without the mic.
Keep up the good work and reporting your findings.
Randy, K7AGE
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These are BAT54 dual diodes according to Farhan Msg #20401 in Yahoogroups. https://www.nxp.com/documents/data_sheet/BAT54_SER.pdf
73 Raj
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I looked it up too before the earlier post. This part has part of the last character missing. Looks like a backwards J. This is an opto isolator chip. Is this what you are talking about Tom?W5KUB? It doesn't make sense to have an opto isolator where a dual diode should be. I haven't seen anything marked BAT54.?
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This will be my first hack. ?Could you write a small commentary on what you actually did in the order you did things, Apart from removing things and stuffing in replacements and adding components are there other connections you need to make? ?It all makes sense to me but I would appreciate a bit more detail. Thank you. Noel
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You'll never see BAT54 printed on a SOT23, that wouldn't fit. ?So they choose an arbitrary 2 or 3 ?character code to distinguish it from all the other SOT23 products they make. ?But there are far more SOT23 types than there are codes, and different manufacturers that build BAT54's will choose different codes. ?We've seen this before on the 2n3904 transistors, read post 19730. ?The ohmmeter readings taken of the bad part suggest that it really is a dual diode. My guess is that the correct part is getting stuffed, but at least one slipped by QC at the factory, got damaged when soldering it down, or by excessive current now that the 100 ohm pot has been removed. ?If it is excessive current, perhaps adding a resistor in series with C106 would fix it. ?Adding back R106 if it isn't needed for establishing modulator balance would best be avoided. ?Not yet clear if this dual diode was a problem on more than one unit. Jerry, KE7ER
On Thu, Feb 9, 2017 at 11:23 am, John Smith wrote: I haven't seen anything marked BAT54.?
?
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Regarding post 19730, there's a couple issues a bit further down that we need to keep track of. 1) ?Q13 is dissipating an awful lot of heat for a Sot23, may need to adjust the emitter resistor there. 2) ?Having your Bitx40 hooked up to an antenna while some nearby antenna is transmitting at high power can blow Q13, may need Raj's dual diode plus lamp fix.
On Thu, Feb 9, 2017 at 12:04 pm, Jerry Gaffke wrote: post 19730 ?
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Don't assume low power out is due to a bad diode pair. The two issues at Q13 mentioned below can both cause a "Possible PA low output problem" that would be indistinguishable from a bad diode pair in the modulator. ?Also could be a a damaged IRF510, perhaps from driving a high SWR load with 20v on the drain, or setting the bias control beyond 100ma quiescent. ?Or the microphone connector got shorted out. ?Or transformer wires shorted or broken. ?Or about half the remaining parts in the rig experiencing some sort of failure.
On Thu, Feb 9, 2017 at 12:19 pm, Jerry Gaffke wrote: Regarding post 19730, there's a couple issues a bit further down that we need to keep track of. 1) ?Q13 is dissipating an awful lot of heat for a Sot23, may need to adjust the emitter resistor there. 2) ?Having your Bitx40 hooked up to an antenna while some nearby antenna is transmitting at high power can blow Q13, may need Raj's dual diode plus lamp fix.
?
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My Q13 seems fine with voltages in-line with Randy's voltage chart. I haven't checked everything yet. From much earlier posts about Q13, it was one of the first things I checked. I am still awaiting conformation from Tom on the part location and part number IL440. It's possible he's wrong. Really need others to confirm and comment. But if it's true I am gonna throw that wrong part into the sun!
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The Vishay datasheet for BAT54 diodes lists the BAT54S SOT-23.
It has a marking "L44".
Note that the common output of this diode pair is where the old pot went (between the diodes).
If using separate diodes, some rearrangement might have to be made.
john
AD5YE
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My DDS BITX40 is now putting out over 5 watts. 1. Ripped out the double diode. 2. Attached 2x ?1N4148 ?diodes (any 2) with the ring ends connected to the empty solder spots for the right orientation. 3. Joined the other ends of the diodes together and soldered them into the empty hole for the missing trimpot ? ?- centre pin hole. 4. Wound the PA bias trimpot to fully clockwise. ?Adjusted slowly to fully anticlockwise and got 0.9A ?with? ? ?no modulation. ?Speaking very loudly, output watt meter on ATU jumping between 5 and 7 watts into dummy load. That's it. ?No more no less Cheers - ?Noel
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What BITX40 needs is a BAT54S - this version has two diodes in opposite
direction. Anode of one connected to cathode of the other.
Marking may be KL4.. or Vishay L44.. or even ?V4
As some one reported IL440 - looks like Vishay, the extra letters and
digits I and 0 may refer to some manufacture details!
Raj
At 10/02/2017, you wrote:
toggle quoted message
Show quoted text
You'll never see BAT54 printed
on a SOT23, that wouldn't fit.? So they choose an arbitrary 2 or
3? character code to distinguish it from all the other SOT23
products they make.? But there are far more SOT23 types than there
are codes, and different manufacturers that build BAT54's will choose
different codes.? We've seen this before on the 2n3904 transistors,
read post 19730.? The ohmmeter readings taken of the bad part
suggest that it really is a dual diode.
My guess is that the correct part is getting stuffed, but at least one
slipped by QC at the factory, got damaged when soldering it down, or by
excessive current now that the 100 ohm pot has been removed.? If it
is excessive current, perhaps adding a resistor in series with C106 would
fix it.? Adding back R106 if it isn't needed for establishing
modulator balance would best be avoided.? Not yet clear if this dual
diode was a problem on more than one unit.
Jerry, KE7ER
On Thu, Feb 9, 2017 at 11:23 am, John Smith wrote:
- I haven't seen anything marked BAT54.
?
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Jerry, I am back at the farm this week. Counting the days to Monday so I
can be reunited with my pup and Bitx40!!
I have received some 3904 SMTs, I propose to put one parallel on top of
the existing Q13 and see how much that helps!
I found an old commercial Motorola Mic in my junk. Just 4 wires and seems
perfectly suited to this board. These mics
have built in mic preamp and thats helping me drive the final amp crazy!
The IRF draws more than 1 amp and power meter
is showing 10W. Must be distorting but I did not have time to check with
scope. Plan to have a QSO with vu2pop
for a critical report on audio etc. this coming week.
The mic seems something like this but the model number is worn out.
I still on analog VFO and it's holding 10-20Hz drift.
Cheers
Raj
At 10/02/2017, you wrote:
toggle quoted message
Show quoted text
Regarding post 19730, there's a
couple issues a bit further down that we need to keep track of.
1)? Q13 is dissipating an awful lot of heat for a Sot23, may need to
adjust the emitter resistor there.
2)? Having your Bitx40 hooked up to an antenna while some nearby
antenna is transmitting at high power can blow Q13, may need Raj's dual
diode plus lamp fix.
On Thu, Feb 9, 2017 at 12:04 pm, Jerry Gaffke wrote:
- post 19730
?
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Raj vu2zap