[TenTec] OMNI V faults help needed!

[Paul]

Sorry for waste of bandwidth, but thought this might be better with a different subject!

Hi Steve.

By lopsided I mean that the action of the PBT control is much smoother on USB than it is on LSB.

In other words, when listening to a USB signal, the PBT control must be at approx 1 o'clock, otherwise severe LF response attenuation occurs.
The same is not so when listening to an LSB signal, where PBT can be left at 12 o' clock without losing LF or HF response, but rotation of PBT anticlockwise results in an unintelligible phone signal at 9 o' clock. The same rotation to 3 o'clock on USB does not result in quite such unintelligibility.
This is with the 2.4KHz filter in use, the "problem" is exacerbated by using the 1.8KHz filter.
There are no 500 or 250Hz filters installed.

My aim is to be able to adjust CIO's or whatever should be adjusted to resolve this admittedly very minor irritation!  

Another 2 minor irritations are:

The RX RF amp seems to "go noisy" for no specific reason.
I noticed that on 40m with a dummy load connected via a 12" patch lead, that the S meter indicated around S3 in  this state, regardless of 40m frequency.
Other bands also exhibited this "raised noise floor", but not as severely as 40m.
I discovered accidentally, that putting my finger near the 4 FET's used as the RX RF amp restored normality, and that physically moving the FET's apart or closer together would "cure" the problem.
I cannot measure anything wrong...
So I believe that the RX RF amp is taking off, or "hooting" or going into self oscillation, pick whichever term suits you!

I have a scope, but so far have not been able to provoke the problem for the scope to look at.

The final minor irritation is the PA on 20m.
For whatever reason, the PA will sometimes "go nuts" ( the only way I can describe it! ) on 20m only, between 14.250 and 14.350.
It is fine into a dummy load, but the PA seems to be VERY picky about even a small amount of reflected power at the top end of 20m. By small, I mean 1.2:1 or about 2% reflected power.
The problem can be "cured" by reducing the output power to 90 watts.. no problem at all then.

This only happens on 20m, and I can "see" when it's happening by watching the ALC led.. in TUNE mode on a dummy load, all is normal at the top end of 20m until RF power out approaches 95 watts. At this point, something flips, the ALC led dims and flickers and a motorboating sound can be heard if monitoring is enabled.

The PSU is not the cause.
I've tried the following, all with exactly the same results:
Astron 35 amp ( RS35 )
HP programmable 0-50v at 100 amps ( forgotten model number )
Home brew 40 amp supply with toroidal transformer.
SEC 1223 SMPSU
Heavy duty car battery ( much to wife's annoyance! )

When I first acquired the Omni V, I had to fix a ground loop that was causing horrible noises to be made by the internal loudspeaker when transmitting.. cured by isolating the small board carrying monitor signals and various adjustable pots from the case.
I was also told that the radio was FM'ing at high power TX. Cured this by bypassing the power connecter and fuseholder on the radio and wiring the power lead direct. Voltage drop through connector and fuse / holder was close to 1 volt.
I use the SEC 1223 PSU with the radio, so bypassing the fuse should be OK. The SMPSU has overcurrent and overvoltage protection.


----- Original Message ----- 
From: "Steve Baron - KB3MM" <SteveBaron at StarLinX.com>
To: <tentec at contesting.com>
Sent: Wednesday, December 24, 2003 4:36 PM
Subject: Re: [TenTec] Why leave out calibration information TT????


> WHat do you mean by lopsided ?
> 
> ----- Original Message ----- 
> From: "Paul" <gw7lhi at hotmail.com>
> To: <tentec at contesting.com>
> Sent: Wednesday, December 24, 2003 13:15
> Subject: Re: [TenTec] Why leave out calibration information TT????
> 
> 
> > I too would like the answer to the question below.
> >
> > I have an Omni V, and would like to investigate the lopsided PBT tuning
> that
> > it has.. but I don't want to do a "screwdrivers expert" job on it in case
> > things worsen :-)
> >
> > So to recap, does anyone know the correct alignment procedure for the
> > Ten-Tec Omni V model 562.
> >
> > I don't really want to make expensive transatlantic phone calls for
> > information that really should be in the manual. My Japanese FT-102 has
> full
> > alignment instructions in the user manual, and it is about the same age as
> > the TT radio.
> >
> > Paul MW0CDO in South Wales UK.
> >
> > Seasons' greetings to all!