|
Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
|
Thread Tools |
16th May 2020, 2:27 pm | #21 |
Triode
Join Date: May 2020
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 18
|
Re: Yaesu FT221 problem with alignment
Tried that but still no joy any other ideas? The mic audio is very quiet also even with the gain right up.
|
16th May 2020, 9:25 pm | #22 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,899
|
Re: Yaesu FT221 problem with alignment
Could the gain right up be overdriving the VOX and causing the sticking in TX mode, but a fault in the modulation drive to the varactor be causing the RF to have very low deviation? High value resistor gone extra-high or a capacitor gone short?
david
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
17th May 2020, 6:20 pm | #23 | |
Triode
Join Date: May 2020
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 18
|
Re: Yaesu FT221 problem with alignment
Quote:
best regards Andy m6yyd |
|
17th May 2020, 11:07 pm | #24 | ||
Triode
Join Date: May 2020
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 18
|
Re: Yaesu FT221 problem with alignment
Quote:
|
||
17th May 2020, 11:32 pm | #25 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,899
|
Re: Yaesu FT221 problem with alignment
Service info should give you normal audio voltages at various places along the chain. Speech isn't a steady enough level nor is whistling. There are apps for smartphones which will make audio tones, but the headphone jack levels will be too high for a microphone input, so you'll need an attenuator (three resistors)
Then you'll need something to measure the level with... oscilloscope, audio millivoltmeter etc. The likelihood is that some component along the chain is sulking there is a steady failure rate of transistors, capacitors and resistors. These things were built with cost-competitive components... mind you, some of the o ce premium components didn't fare much better. Electrolytic capacitors use water-based conductive fluid in them as one of their electrodes. Over time water leaves as vapour past the seals. It just needs a slightly iffy rubber seal or a bit of muck and they fail without needing high temperatures to accelerate them. So it's simple spadework. Apply a signal and follow it along, checking levels, to get the fault down to an area, then start focusing in on the problem. The audio path may have some AGC to correct for microphone levels, there may be a compressor or speech processor. So it may be a bit more complex than just a couple of amplifiers and a gain pot. One quick check would be to substitute a known good microphone. You never know. David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
18th May 2020, 8:26 pm | #26 | |
Triode
Join Date: May 2020
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 18
|
Re: Yaesu FT221 problem with alignment
Quote:
|
|
18th May 2020, 8:32 pm | #27 |
Triode
Join Date: May 2020
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 18
|
Re: Yaesu FT221 problem with alignment
evening everyone, would anyone have any ideas what transistor the one in this circuit is or what i could use to replace it, thinking about creating the above circuit on stripboard to replace the LD3001 IC mic pre amp circuit.
Best Regards Andy M6YYD |
18th May 2020, 9:38 pm | #28 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,899
|
Re: Yaesu FT221 problem with alignment
You should be able to get away with murder with that transistor.
Something with high Hfe at a few mA and a reputation for reasonably good noise. Something fairly jellybean 2N3904/MMBT3904 in through-hole or SMT formats is a jack of all trades. In circuit complexity terms going to an opamp isn't going to be any easier. I'd just stick with the original circuit. David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
19th May 2020, 12:00 am | #29 | |
Triode
Join Date: May 2020
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 18
|
Re: Yaesu FT221 problem with alignment
Quote:
See the pictures of the board I've created what do you think Best regards andy M6YYD |
|
19th May 2020, 1:13 am | #30 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,899
|
Re: Yaesu FT221 problem with alignment
Given that circuit and the size of the thing, it was probably a hybrid... an SMT transistor Or chip transistor, chip capacitors and thick film resistors fired on a ceramic substrate.
There was a fashion for sticking common analogue circuits on them, but the predicted advantages and cost savings were proven a bit optimistic. David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
19th May 2020, 8:30 am | #31 | |
Triode
Join Date: May 2020
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 18
|
Re: Yaesu FT221 problem with alignment
Quote:
The other components capacitors etc are allready around the ic on the board as through hole Best regards Andy M6YYD |
|
19th May 2020, 8:51 am | #32 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,899
|
Re: Yaesu FT221 problem with alignment
Ought to be fine.
David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
19th May 2020, 11:35 am | #33 |
Triode
Join Date: May 2020
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 18
|
Re: Yaesu FT221 problem with alignment
|