On Dec 27, 2006, at 5:27 PM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Dec 27, 2006, at 12:24 PM, pentalab wrote:

### Owner's can avoid the parasitic problem altogether by simply
removing the 2 x rf chokes from the gid pins... plus the 6 x 200pf
caps from the same grid pins..... and then directly ground the

6 grid pins

with wide strap. Then the stock suppressor's will work

just fine.

## By semi-floating the grids you are just asking for parasitic

trbl.

RICH SEZ... According to my dipmeter, directly-grounding a 3-500Zs
grid pins makes little difference in the grid's resonant frequency.

The AL-82 is as unstable as are the TL-922 and SB-220, yet the
AL-82 has directly-grounded grids.

Jim -- How long is the grid grounding strap for a 3-500Z ?

#### The AL-82...and it's little bastard brother.. the AL-80BX are
two of the most parasitic prone amps in existence.... which is why
the east coast guys call em the "fire cracker". So even though both
have their grids tied directly to chassis... Ameritron has still
managed to screw em both up.

The VHF suppressors in the SB-220, AL-82, and the TL-922 have a Q of 4.5 to 5.5 at 100MHz,and all have a reputation for squirreliness. If direct-grounding the grids is the sure cure for VHF instability, why isn't the one with direct-grounded grids stable?

### I think the straps I used in my L4B's are 1/2" wide cu... and
as short as practical. I can name u 12 guys I know who directly
grounded the grid's on TL-922's.... and all reported the same
results... and 100+ more who directly grounded the grids on SB-
220/221's. ..same deal.... same results. Rock stable.... and 20-
25 watts less drive required.... using stock suppressors. And don't
feed us this crap about a 200 pf disc ceramic having less L than a
1/2" wide solid CU strap.... it doesn't.

A 200pF cap with short, shorted leads dips at c. 130MHz. At 100MHz, it has a small amount of negative reactance. At 100MHz, a 1/2" wide Cu strap 1" long has c. 65-ohms of positive reactance. At 100MHz, which has more inductive reactance, the cap or the strap?

### Why the grid resonance doesn't change much... who knows.

It doesn't change much because 1/2" (12.7mm) strap does Not have half the inductance per unit length that 1/4" (6.35mm) strap has. According to Terman, inductance is a logarithmic function of width. Thus, if Terman is right, there is not a lot of difference in inductance between 10" (254mm) of #14 Cu wire and 10" of 2"-wide Cu strap. To experimentally see the difference, one can alternately connect 10" of #14, and 10" of 2" strap across a 50 to 100 pF doorknob cap and measure each resonant frequency with a dipmeter. From these measurements, one can calculate the inductance of the #14 and the inductance of the 2" strap. I have the needed materials to perform this experiment. Would anyone like to venture a guess as to how much less L the 2" strap exhibits than the #14 wire?

Why
the drive requirements drop 20-25 watts on every band.... who
knows.

Unless there is zero reflected power and the power meter has recently been calibrated, power meter measurements are untrustworthy.

... Why u insist on semi floating the grids on a GG amp is
beyond me.

The grids are not floating at 100MHz with cap-grounding. Because the cap's negative reactance cancels some of the grid's inductance, the grids have a less +j-ohms path to ground at 100MHz than is afforded by Cu straps. Thus, cap-grounding slightly increases the grid's resonant frequency and allows for grid fusing.

...
R. L. Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

On Dec 27, 2006, at 5:32 PM, Mike(W5UC) & Kathy(K5MWH) wrote:

I'm not familiar with this amp, but a good guess is that I would look for a shorted diode or diodes in the power supply.

If a HV rectifier diode shorts, and the electrolytics are not protected from AC by reverse diodes, the electrolytics are DOA.

...

R. L. Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

On Dec 27, 2006, at 5:27 PM, Vernon J. Kunes, Jr. wrote:

The problem at this time is that the amp takes out the 10 amp fuses
when I turn it on. High voltage problem?

Probably. With the tube in or out?

R. L. Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

I'm not familiar with this amp, but a good guess is that I would look for a shorted diode or diodes in the power supply.

73,
Mike, W5UC



At 07:27 PM 12/27/2006, you wrote:

The problem at this time is that the amp takes out the 10 amp fuses
when I turn it on. High voltage problem?

--- In ham_amplifiers@..., R L Measures wrote:
>
>
> On Dec 27, 2006, at 12:31 PM, Tony King - W4ZT wrote:
>
> > The AL-80A manual can be downloaded from
> > <> or a paper copy can be obtained
> > directly from Ameritron.
> >
> > pentalab wrote:
> > > --- In ham_amplifiers@..., R L Measures wrote:
> > >> Hi, Vernon
> > >> .
> > >> 6. inspect the 10m and 15m L, plus the 80m & 160m Tune-C-padder
> > >> bandswitch contacts.
> > >
> > > ##### Rich.... do they actually pad the C1 tune cap on 160 + 80m
> > > on a AL-80 B ??? I can understand maybe padding the C1 cap on
> > > 160m... but not 80m.
> >
> > The schematic shows padding C1 on 160 meters only but padding C2 on
> > 160,
> > 80 and 40 meters.
>
> Sorry, Jim. My mistake.
> >
> > >
> > > ### I think they pull the same stunt on the TL-922 on at least
> > 160m ?
> > >
>
> The 922 uses Tune-C padders on 160m and 80m.
> > > ## I can see now where these amps could easily give plenty of trbl.
> > > There is one heluva lot of RF on a tune cap as is.
> > >
> > > ### padding a load cap is no big deal... padding a tune cap is a
> > > big deal.
>
> agreed
> > >
> > > Later... Jim VE7RF
> > >
> >
>
> R. L. Measures, AG6K, 805.386.3734
> r@..., rlm@...,
>

"age & treachery will overcome youth & skill"

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Dec 27, 2006, at 12:24 PM, pentalab wrote:

### Owner's can avoid the parasitic problem altogether by simply
removing the 2 x rf chokes from the gid pins... plus the 6 x 200

pf

caps from the same grid pins..... and then directly ground the 6

x

grid pins with wide strap. Then the stock suppressor's will work
just fine.

## By semi-floating the grids you are just asking for parasitic
trbl.

RICH SEZ... According to my dipmeter, directly-grounding a 3-500Zs
grid pins makes little difference in the grid's resonant frequency.

The AL-82 is as unstable as are the TL-922 and SB-220, yet the
AL-82 has directly-grounded grids.

Jim -- How long is the grid grounding strap for a 3-500Z ?

#### The AL-82...and it's little bastard brother.. the AL-80BX are
two of the most parasitic prone amps in existence.... which is why
the east coast guys call em the "fire cracker". So even though both
have their grids tied directly to chassis... Ameritron has still
managed to screw em both up.

### I think the straps I used in my L4B's are 1/2" wide cu... and
as short as practical. I can name u 12 guys I know who directly
grounded the grid's on TL-922's.... and all reported the same
results... and 100+ more who directly grounded the grids on SB-
220/221's. ..same deal.... same results. Rock stable.... and 20-
25 watts less drive required.... using stock suppressors. And don't
feed us this crap about a 200 pf disc ceramic having less L than a
1/2" wide solid CU strap.... it doesn't.

### Why the grid resonance doesn't change much... who knows. Why
the drive requirements drop 20-25 watts on every band.... who
knows. All I know from repeated tests... and having done it
umpteen times is [a] drive drops 22 watts [b] stabilty is
enhanced [c] IMD is improved.... then improved again.. since xcvr
output can be reduced by 20-25 watts.

### I'm 100% convinced that parasitic stability starts with how
well the grids are bonded to the chassis. I'd bond the grids to
chassis... then if amp is still squirelly... proceed with a fix....
whether that involves using a small globar.. or nichrome.. is a moot
point. It's worth it just for the decreased drive.

### The TL-922 owner's who had nichrome suppressor's in em...
reported they could replace em with stock kenwood suppressors... and
the amp was stable. .... provided the grids were directly
grounded. Why u insist on semi floating the grids on a GG amp is
beyond me.

Jim VE7RF

Later... Jim VE7RF

R. L. Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

The problem at this time is that the amp takes out the 10 amp fuses
when I turn it on. High voltage problem?

On Dec 27, 2006, at 12:31 PM, Tony King - W4ZT wrote:

The AL-80A manual can be downloaded from
<> or a paper copy can be obtained
directly from Ameritron.

pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

Hi, Vernon
.
6. inspect the 10m and 15m L, plus the 80m & 160m Tune-C-padder
bandswitch contacts.

##### Rich.... do they actually pad the C1 tune cap on 160 + 80m
on a AL-80 B ??? I can understand maybe padding the C1 cap on
160m... but not 80m.

The schematic shows padding C1 on 160 meters only but padding C2 on 160,
80 and 40 meters.

Sorry, Jim. My mistake.

### I think they pull the same stunt on the TL-922 on at least

160m ?

The 922 uses Tune-C padders on 160m and 80m.

## I can see now where these amps could easily give plenty of trbl.
There is one heluva lot of RF on a tune cap as is.

### padding a load cap is no big deal... padding a tune cap is a
big deal.

agreed

Later... Jim VE7RF

R. L. Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

On Dec 27, 2006, at 12:24 PM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

? As I understand it, Trio-Kenwood has stopped selling bandswitches
for the TL-922. The stock TL-922 uses VHF parasitic suppressors with
a Q of c. 5.5 @ 100MHz. Since the the TL-922's original suppressors
with a pair of fresh 3-500Zs can produce intermittent oscillations

c.

120MHz which can arc, melt & even evaporate the 10m and 15m L
contacts on the bandswitch, owners can avoid the problem by either
switching to lower-Q VHF suppressors to lower VHF-gain, or by using
worn-out 3-500Zs to do the same.
- end

### Owner's can avoid the parasitic problem altogether by simply
removing the 2 x rf chokes from the gid pins... plus the 6 x 200 pf
caps from the same grid pins..... and then directly ground the 6 x
grid pins with wide strap. Then the stock suppressor's will work
just fine.

## By semi-floating the grids you are just asking for parasitic
trbl.

According to my dipmeter, directly-grounding a 3-500Zs grid pins
makes little difference in the grid's resonant frequency.
The AL-82 is as unstable as are the TL-922 and SB-220, yet the
AL-82 has directly-grounded grids.

Jim -- How long is the grid grounding strap for a 3-500Z ?

Later... Jim VE7RF

R. L. Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

Except being a tetrode with same anode dissipation there is nothing
equivalent

73
Peter

________________________________

From: ham_amplifiers@... [mailto:ham_amplifiers@...]
On Behalf Of R L Measures

As I understand it, the GU-95B is equivalent to the 5cx5000A / 8170.

The AL-80A manual can be downloaded from <> or a paper copy can be obtained directly from Ameritron.

pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

Hi, Vernon
.
6. inspect the 10m and 15m L, plus the 80m & 160m Tune-C-padder bandswitch contacts.

##### Rich.... do they actually pad the C1 tune cap on 160 + 80m on a AL-80 B ??? I can understand maybe padding the C1 cap on 160m... but not 80m.

The schematic shows padding C1 on 160 meters only but padding C2 on 160, 80 and 40 meters.

### I think they pull the same stunt on the TL-922 on at least 160m ?
## I can see now where these amps could easily give plenty of trbl. There is one heluva lot of RF on a tune cap as is.
### padding a load cap is no big deal... padding a tune cap is a big deal. Later... Jim VE7RF

73, Tony W4ZT

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

? As I understand it, Trio-Kenwood has stopped selling

bandswitches

for the TL-922. The stock TL-922 uses VHF parasitic suppressors

with

a Q of c. 5.5 @ 100MHz. Since the the TL-922's original

suppressors

with a pair of fresh 3-500Zs can produce intermittent oscillations

c.

120MHz which can arc, melt & even evaporate the 10m and 15m L
contacts on the bandswitch, owners can avoid the problem by

either

switching to lower-Q VHF suppressors to lower VHF-gain, or by

using

worn-out 3-500Zs to do the same.
- end

### Owner's can avoid the parasitic problem altogether by simply
removing the 2 x rf chokes from the gid pins... plus the 6 x 200 pf
caps from the same grid pins..... and then directly ground the 6 x
grid pins with wide strap. Then the stock suppressor's will work
just fine.

## By semi-floating the grids you are just asking for parasitic
trbl.

Later... Jim VE7RF

R. L. Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

Hi, Vernon
.
6. inspect the 10m and 15m L, plus the 80m & 160m Tune-C-padder
bandswitch contacts.

##### Rich.... do they actually pad the C1 tune cap on 160 + 80m
on a AL-80 B ??? I can understand maybe padding the C1 cap on
160m... but not 80m.

### I think they pull the same stunt on the TL-922 on at least 160m ?

## I can see now where these amps could easily give plenty of trbl.
There is one heluva lot of RF on a tune cap as is.

### padding a load cap is no big deal... padding a tune cap is a
big deal.

Later... Jim VE7RF

On Dec 27, 2006, at 11:24 AM, Frank Goenninger wrote:

Hi all:

There are several GU-95B available on ebay - I am about to decide to
buy one if these to upgrade to > 6 kW out. I have been looking on the
net for a datasheet but have been unable to find one.

Hi, Frank
As I understand it, the GU-95B is equivalent to the 5cx5000A / 8170.

Is there any source known to you guys? And of course I'd like to hear
any comments on experience of using the GU-95B in AB1 grid-driven
service ...

The hurdle for a 4cx5000A in AB1 is the grid/Bruene-bridge neutralization circuitry. This subject is covered on:


If you used a 4cx10,000D, you would have the same tube with the added benefit of a more efficient anode cooler.

end

Thx!

73, Frank DG1SBG

R. L. Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

Hi all:

There are several GU-95B available on ebay - I am about to decide to buy one if these to upgrade to > 6 kW out. I have been looking on the net for a datasheet but have been unable to find one.

Is there any source known to you guys? And of course I'd like to hear any comments on experience of using the GU-95B in AB1 grid-driven service ...

Thx!

73, Frank DG1SBG

? As I understand it, Trio-Kenwood has stopped selling bandswitches
for the TL-922. The stock TL-922 uses VHF parasitic suppressors with
a Q of c. 5.5 @ 100MHz. Since the the TL-922's original suppressors
with a pair of fresh 3-500Zs can produce intermittent oscillations c.
120MHz which can arc, melt & even evaporate the 10m and 15m L
contacts on the bandswitch, owners can avoid the problem by either
switching to lower-Q VHF suppressors to lower VHF-gain, or by using
worn-out 3-500Zs to do the same.
- end

R. L. Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

Hi, Vernon
--- I would:
1. remove the tube.
2. measure the filament/grid BDV with a high pot. <5kV is not okay.
3. fire the amp up without the tube and make sure the HV is normal.
4. check the meter accuracy, esp. the grid-I and anode/plate-I.
5. unsolder one end of the VHF suppressor R from L-supp and measure its resistance.
6. inspect the 10m and 15m L, plus the 80m & 160m Tune-C-padder bandswitch contacts.
7. if the R in #4 is more than 50% high, and/or if there are burned bandswitch contacts, it might be a good idea to decrease the VHF-Q of the VHF suppressor.
8. Add a 120J 10-ohm to 20-ohm glitch R in series with the HV+.

end


On Dec 26, 2006, at 5:24 PM, Vernon J. Kunes, Jr. wrote:

I need a clear, crisp copy of the schematic for an AL80-A. It is dead
and I am going to attempot a fix. Any help will be appreciated.


...

R. L. Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

I meant to send this earlier. I hope everyone had a very Merry Christmas and wishing you a Happy new Year. Many thanks for the help in 2006.

Garry - WR4R

I need a clear, crisp copy of the schematic for an AL80-A. It is dead
and I am going to attempot a fix. Any help will be appreciated.

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