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Washington 858pll low power

liquidh8

liquidh8

Active Member
Aug 7, 2011
273
8
28
:mad:Ok Guys. I have a Washingotn, 858PLL. @ off them actually, my old one is now a parts radio for this one. When I got it it only did like 8 watts PEP, My old one did 21 with the 1307 final, But I drove it low at 12. ( I kow what they are rated for). Anyway, this one had all sorts of noise toys and the unlocked clarifier, and channels. needless to say it was a hacked mess. After getting the frequency expansion right, new mic jack, new driver (2166), final(efl20W), regulators, power suppy caps, recieve mods, alignment on tx/rx. It will do 11 watts PEP, no more. I am told the audio is a bit muffled.

I tried different mics, removed the compressor circuit, changed the predriver FET, broadbanded it, un broadbanded it, lol.
Started changing caps one by one.
I tried a different relay I mean I am at a loss as to why it is only putting out half power.
It has 13.8 Vdc steady under TX with the rebuilt powersupply board.
The driver and final get 13.8 under TX on SSB, bias seems right.
I dunno, suggestions? Some where to start probing?

73's and thanks

231 PA
 

Maybe a shot in the dark but look at the ALC circuit, caps may have dried up.
 
That is what i started to do. I even swapped out the modulation x-former, just because it it high resistance readings than the one that was in there. The driver and finals are getting the voltage from the power supply it seems. I check at the test points to make sure, so that tells me the relay, mode switch, power supply and associated traces are good. I just don't know why it is only putting out 1 watts, and that is with a whistle. It swings around talking at about 5 watts. (SSB), AM is a bit less. I can get a higher DK, but not much swings. (stock audio circuit anyhow).

Jim

231 PA
 
Ok, I got out there last night and played around some more. I went over the alignment specs again, checked all the diodes, looked for messed up traces, etc. Then it occured to me, how much power does it make at other frequencies? It has channels in it, I redid the channel hack from when I got it. I used a 6 POS rotoary switch, and a SPST for the missing one, ie 27.415, 425, 435, 445. So at 27.999, It makes 19-21 watts PEP! At 26.500 it make like 18. No amount of adjustment of the cans will balance the power out. It is always high at both extremes. Adjusting the cans does change the output though, just not evenly.

L37 is broadbanded. I tried it with just jumpers, with the disc cap. I tried unbroadbanding it, it just doesn't make the power in the area I talk on. i.e. 27.165 to 27.555. And, I am told i sound a bit muffled, 4 different mics havent cured that either. I HAVE to be missing something, or, something got messed from the prior channel hack.

When I say hack, they took out all the CT's for the AM, LSB, USB adjustments, the unlocked clarifier was Half assed, resistors were missing, it was in frequency nomans land, I didn't know where I was ever at!

I am going to put the frequency range back to stock and see what it does, but I don't think that is going to change anything.

Anyone?
 
I never knew the 858 pll chassis had a audio compressor. is that why i never need to run a power mic on my teaberry stalker 1 and my 449????
 
I believe so, every power mic i try on my Washingtom doesn't sound real good, it's always too much.

OK, Update, a good one. I got out there tonight and took a fresh mind to it. I replaced the ceramic caps by the tx tuning cans, l37, l34, etc. I unbroadband the radio. That got it a little better. Then, I put stock 1306 and 1307 driver/final in it, that didn't change anything. I changed all the rest of the electrolytic caps a few at a time as some were right next to the other, and after all the caps were in it, I reset the bias, and now it gets 16/17 watts PEP SSB. The 1307 is rated for 16 watts, I am happy.

So, it was a collection of things I guess, I am going to leave it unbroad banded since I only really inten to use it from 27.165 to 27.555, I tuned it for around there. And I am driving a KLV550 with it so it need not be any higher in power.

I also put the audio compression circuit back in it because i like it.
Thanks for all the input guys!
 
I only talked t to a friend last night who was 24 miles away. So it was hard to get a true audio check. What are you suggestions?
 
Well, I talked to the same friend who heard it before, and he said it sounds great. After going thru the TX balance procedure, I am happy with 18-20 watts PEP, but I have it turned back down some. I have to get a good noise cancelling mic though, the mic circuit is super sensitive, just like the other, lol.
So what were some of those tricks/tips you had?
 
The D858 SSB chassis has its own seperate transistor to limit the ALC, which is TR16. R72 connects the emitter of TR16 to ground. It's a 470 ohm resistor. For my tastes, this value is too low, and doesn't allow the transistor to limit the ALC enough to allow the flexibility to use a wide range of microphones. I changed mine to a 1k ohm, but anything from 1k to 2.2k would work great. This allows TR16 to limit the ALC a little better.

The second mod I did was this:

Locate the audio wire coming off the Microphone jack (will be a 2 conductor wire, shield with a center conductor, center conductor is white) and trace it to where it solders onto the PCB (which falls in the area of C201, thereabouts, on the bottom side of the PCB), solder the 470 ohm resistor that you (may have) pulled from R72, from where your audio wire is soldered onto the PCB to PCB ground. Basically, you're putting a 470 ohm resistor from your audio wire to ground. This also will also act as a limiter of sorts, and will result in a cleaner sounding radio. The second mod is optional. This mod works best if you're planning on using an amplified desk microphone, like a D104, or a Turner +3/+3B/Super Sidekick. For a stock mic, the first mod above should be plenty.

Another mod I have used that works well, is to lift the banded end of D46 (most people just clip this diode, it disables CT7, the trimmer capacitor that adjusts SSB output... that's a no-no) and install a 220 ohm 1/4 watt resistor inline on the banded side (cathode) of D46. This "opens" up the SSB output while retaining full adjustability of CT7.

Hope these mods will assist you!


~Cheers~
 
Awesome, thank you for sharing the info! I am glad you hopped in here!. Now a few questions.

Mod one, sounds great, I am going to try it. The mic is so sensative, a stocker, I have to run the gain at about 1/4.

Mod two. Would raising the value or R107 help out here? It is a 5W cement resistor. This Washington has a 4.7 ohm there, the parts one has a 10 ohm. Just curious. The 139xlr parts list shows the 10 ohm.

Mod 3. Looking at the schematic, there is a 10k resistor in parallel with D46, R171. Could we just replace r171 with said 220 ohm? Wouldn't R171 end up looking like 215 ohms anyway with the resisted paralled there? Or am I missing something, since the the 220 ohm would be in series with d46, then both in parallel with r171?

I am just curious, I have the 139xlr schematic here in work, and the radio is home so I'll be trying them out later.

This radio has got tons of SSB audio, But it is kinda too much. especially when in from of the KLV550, lol.
 
Heya!

Changing R107 won't change anything as far as transmit goes, that's only going to affect receive audio. The 4.7 ohm is updated from the 10 ohm.


For D46, you want to put the 220 ohm in series with it. Don't touch R171. Putting that 220 ohm on the cathode side of D46 reduces flow thru D46.

Mod #2 allows you to have more control of the mic on top of Mod #1. On my President washington, the combination of all 3 mods, allows me to run my mic gain wide open while using a D104, and it doesn't sound muffled or dirty.

~Cheers~
 
Ahh, ok, after posting I figured that for the r107, just to make the speaker louder.

It's been alot of years since college, so some electronics principle slip my mind,lol. But, I appreciate this info!

I have a d104 built, (not d104 anymore), that has a high gain amplifier, and an adjustable compression circuit built in, maybe too much for this radio though.

I also have a heavily modified CA-75 cobra power mic I may run with this. I'll be trying these tonight I think when i get home.

(y)(y)
 

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