Great info carl. I think I will also rebuild the input tuned ckt with new
caps.
The idle current is about 90 in CW and ~125 in SSB. The HT pulls about 300V
on full CW drive. I guess I have to work on the filter caps. BTW Just
ordered a new pair of 4-400 ... easily available at a very cheap price (~
25$ for a good pull).
I am thinking of driving the boot with EB63 directly... fitting it under the
chassis this will give me ~ 130 PEP that should be more than what i need...
will also avoid the input mismatch as the base impedance variation in
transistor pa is much smaller than the cathode impedance.
Regards /// Rahul
On Fri, Sep 11, 2009 at 8:10 PM, Carl <km1h@jeremy.mv.com> wrote:
> The 10, 15, and 40M coils have to be from the SB-220 as well as their
> matching caps.
>
> The part # is stamped on all coils and the ones you should have are:
>
> 10M 40-964
> 15 40-964 uses different caps
> 40 40-966
>
> The 20M coil is 40-965 in both versions as is the 40-1012 for 80M. The 20M
> input cap is 220pf and the output 180pf.
>
> BTW, what is the idle current in both mode positions? Dont know if thats
> been covered.
>
> Carl
>
>
> ----- Original Message -----
> *From:* Rahul Sathe <vu3raz@gmail.com>
> *To:* Carl <km1h@jeremy.mv.com>
> *Sent:* Thursday, September 10, 2009 9:06 PM
> *Subject:* Re: [Amps] SB221 Low Power Help
>
> VSWR much better on other bands, Do not have FL1, I am not sure about the
> coils though, I will have to take them out and check.
>
> Rahul
>
>
> On Thu, Sep 10, 2009 at 11:01 PM, Carl <km1h@jeremy.mv.com> wrote:
>
>> It sounds like somone smoked the input in the past. Is the VSWR good on
>> other bands now? Does it still have the FL-1 filter installed? If not have
>> the coils been replaced with SB-220 versions?
>>
>> Excessive drive will destroy the tiny tuning cores in the coils. I can
>> supply good used coils with caps for either model at $5 each + postage.
>> Removed during 6M conversions.
>>
>> Carl
>>
>>
>>
>> ----- Original Message -----
>> *From:* Rahul Sathe <vu3raz@gmail.com>
>> *To:* Carl <km1h@jeremy.mv.com> ; amps@contesting.com
>> *Sent:* Thursday, September 10, 2009 1:12 PM
>> *Subject:* Re: [Amps] SB221 Low Power Help
>>
>> Great ! Just replaced a flaked input cap... VSWR still off the scale on
>> 20, still with 100 W CW the loading has improved to 500mA @ 2500V 400 mA
>> with RTTY 2 tone. I guess that will be the top limit of the wimpy PSU.....
>>
>> Also found that one of the 4-400s is dud (need to get another one) so the
>> tube replacement test is postponed.
>>
>> Rahul
>> On Thu, Sep 10, 2009 at 10:24 PM, Carl <km1h@jeremy.mv.com> wrote:
>>
>>> It all depends on plate voltage and the brand of tube. It was never
>>> designed for GG so it hasnt been characterized until much later. My newest
>>> Eimac spec sheet is a 1966 revision and the 3-400Z was already on the
>>> market.
>>>
>>> You will have to experiment.
>>>
>>> Directly grounding the grids will give a bit more output, result in less
>>> stability and result in around 3 dB worse IMD in dynamic voice tests (not a
>>> static 2 tone)
>>>
>>> Carl
>>>
>>>
>>>
>>> ----- Original Message -----
>>> *From:* Rahul Sathe <vu3raz@gmail.com>
>>> *To:* Carl <km1h@jeremy.mv.com>
>>> *Sent:* Thursday, September 10, 2009 9:42 AM
>>> *Subject:* Re: [Amps] SB221 Low Power Help
>>>
>>> Carl,
>>> I think the 4-400 is Zero Bias, do I still need a string of diodes or if
>>> just bypass the zener it should work ?
>>>
>>> I also seen people suggesting to ground the grids of 3-500 to reduce the
>>> drive requirements and this will increase IMD.. I am a bit skeptical. I will
>>> have to test IMD on a Spectrum Analyzer before i can really ground the grids
>>> directly. Have you ever grounded the grids directly? what effect it has?
>>>
>>> Too many questions, I hope i am not too curious ;)
>>>
>>> Regards /// Rahul
>>>
>>> On Thu, Sep 10, 2009 at 6:26 PM, Carl <km1h@jeremy.mv.com> wrote:
>>>
>>>> The 4-400A requires a little bit more drive than the 3-500 so the
>>>> grids can be directly grounded if you wish. 100W drive should still give
>>>> 1000W+ out in SSB position.
>>>>
>>>> Carl
>>>>
>>>>
>>>>
>>>> ----- Original Message -----
>>>> *From:* Rahul Sathe <vu3raz@gmail.com>
>>>> *To:* Carl <km1h@jeremy.mv.com>
>>>> *Sent:* Wednesday, September 09, 2009 10:09 PM
>>>> *Subject:* Re: [Amps] SB221 Low Power Help
>>>>
>>>> Thanks carl, I have already replaced the stock fan with a high speed
>>>> high volume fan. What about the grid chokes? I guess 4-400 do not need
>>>> them?
>>>>
>>>> Regards /// Rahul
>>>>
>>>> On Thu, Sep 10, 2009 at 7:24 AM, Carl <km1h@jeremy.mv.com> wrote:
>>>>
>>>>> Enough to obtain the same idle current. The zener can be replaced by
>>>>> a reverse string of 1N5408's and the correct number by experimenting.
>>>>>
>>>>> If you intend to run them at full power another fan should be used as
>>>>> its not adequate at 50 Hz. Harbach sells a high speed replacement in the
>>>>> US
>>>>> which is ideal for graphite plates and should be OK in India also.
>>>>>
>>>>> Off to bed.
>>>>>
>>>>> Carl
>>>>>
>>>>>
>>>>> ----- Original Message -----
>>>>> *From:* Rahul Sathe <vu3raz@gmail.com>
>>>>> *To:* Carl <km1h@jeremy.mv.com>
>>>>> *Sent:* Wednesday, September 09, 2009 9:37 PM
>>>>> *Subject:* Re: [Amps] SB221 Low Power Help
>>>>>
>>>>> Carl
>>>>> How much bias I need on 400s? any other changes required for long term
>>>>> use, ls 130V cut off ok?
>>>>>
>>>>> Rahul
>>>>>
>>>>> On Thu, Sep 10, 2009 at 7:01 AM, Carl <km1h@jeremy.mv.com> wrote:
>>>>>
>>>>>> The 4-400's will at least tell you if something dramatic changes
>>>>>> with the power. Its better than spinning wheels working in the input. Get
>>>>>> the most obvious fault out of the way first.
>>>>>>
>>>>>> They may require a bias change for long term use but not just to test.
>>>>>> No socket changes. Filaments are identical.
>>>>>>
>>>>>> Carl
>>>>>>
>>>>>>
>>>>>>
>>>>>> ----- Original Message -----
>>>>>> *From:* Rahul Sathe <vu3raz@gmail.com>
>>>>>> *To:* Carl <km1h@jeremy.mv.com>
>>>>>> *Sent:* Wednesday, September 09, 2009 8:45 PM
>>>>>> *Subject:* Re: [Amps] SB221 Low Power Help
>>>>>>
>>>>>> Carl,
>>>>>>
>>>>>> I have few brand new european 4-400 s however I have not got time to
>>>>>> test them in the amp. With a normal Idle current in the present 3-500s I
>>>>>> would first try and look in the input circuit.. I still suspect that the
>>>>>> 100
>>>>>> W is not reaching the cathode... if it does not work.. i will replace
>>>>>> the
>>>>>> tubes with 4-400, but I do not know if I can "just replace" them.
>>>>>>
>>>>>> Regards /// Rahul
>>>>>>
>>>>>> On Wed, Sep 9, 2009 at 11:10 PM, Carl <km1h@jeremy.mv.com> wrote:
>>>>>>
>>>>>>> Id be suspecting the tubes by now but dont know if you have access
>>>>>>> to any in India. 4-400's or Euro equivalents can also be used in a
>>>>>>> "pinch"
>>>>>>> and the input realigned as needed.
>>>>>>>
>>>>>>> Carl
>>>>>>> KM1H
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> ----- Original Message -----
>>>>>>> *From:* Rahul Sathe <vu3raz@gmail.com>
>>>>>>> *To:* Carl <km1h@jeremy.mv.com>
>>>>>>> *Sent:* Tuesday, September 08, 2009 9:13 PM
>>>>>>> *Subject:* Re: [Amps] SB221 Low Power Help
>>>>>>>
>>>>>>> Carl, No sign of melted contacts on the switch. The chokes are equal
>>>>>>> spaced and not open. the caps look ok on a VTVM no leakage (I still
>>>>>>> think
>>>>>>> these need replacement). Will replace these soon.
>>>>>>>
>>>>>>> One of the Caps in the drive chain, on the cathode found to be
>>>>>>> flaking along the leads when i moved it now replaced it with a
>>>>>>> new....will
>>>>>>> test it today evening after morning qth work. if things are same then
>>>>>>> time
>>>>>>> to move to internal coax.
>>>>>>>
>>>>>>> Gerald, I fully agree with you. I am not in a favor of using the ATU
>>>>>>> as the purpose of having a built in ATU is totally different. I used to
>>>>>>> have
>>>>>>> a HW 101, I also think that it would have been easy to match and drive
>>>>>>> 220 /
>>>>>>> 221 with its sibling easily.
>>>>>>>
>>>>>>> Regards /// Rahul
>>>>>>>
>>>>>>> On Wed, Sep 9, 2009 at 12:41 AM, Carl <km1h@jeremy.mv.com> wrote:
>>>>>>>
>>>>>>>> Grounding the grids isnt any help.
>>>>>>>>
>>>>>>>> With that idle it appears that both tubes are working to some
>>>>>>>> degree.
>>>>>>>>
>>>>>>>> The grid chokes are 3 pie's and should be equally seperated. It they
>>>>>>>> are touching it is a sign of a tube gas arc. Also carefully inspect
>>>>>>>> all 6
>>>>>>>> grid capacitors for cracking. If you have a good analog VOM or VTVM
>>>>>>>> check
>>>>>>>> for leakage.
>>>>>>>>
>>>>>>>> Carefully look at the input and output switch for melted contacts.
>>>>>>>>
>>>>>>>> If the power falls off as frequency goes up that is often a sign of
>>>>>>>> weak tubes. Do you know the history of the amp? When did it last work
>>>>>>>> 100%?
>>>>>>>>
>>>>>>>> Carl
>>>>>>>> KM1H
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> ----- Original Message -----
>>>>>>>> *From:* Rahul Sathe <vu3raz@gmail.com>
>>>>>>>> *To:* Carl <km1h@jeremy.mv.com> ; amps@contesting.com
>>>>>>>> *Sent:* Tuesday, September 08, 2009 1:39 PM
>>>>>>>> *Subject:* Re: [Amps] SB221 Low Power Help
>>>>>>>>
>>>>>>>> Carl,
>>>>>>>> Plate Idle Current in SSB position is ~ 120 to 125 mA. I have to
>>>>>>>> check the grid chokes as suggested by you, how abt grounding the grids
>>>>>>>> directly without chokes?
>>>>>>>>
>>>>>>>> Checked the tubes... there is no short.
>>>>>>>> The coaxial cables looks ok, as the VSWR is far better on other
>>>>>>>> bands like 40 and 80 input can be tuned on 40 and 80.
>>>>>>>>
>>>>>>>> Will run the amp with individual tubes as suggested by dan.
>>>>>>>> I am not sure if it is a European build, however it is wired for 230
>>>>>>>> V no way to find out if it has 50Hz transformer.
>>>>>>>>
>>>>>>>> Thanks for all the help.
>>>>>>>>
>>>>>>>> Regards /// Rahul
>>>>>>>>
>>>>>>>> On Tue, Sep 8, 2009 at 10:50 PM, Carl <km1h@jeremy.mv.com> wrote:
>>>>>>>>
>>>>>>>>> A couple of things to check Rahul:
>>>>>>>>>
>>>>>>>>> 1. Plate idle current should be 120-150 ma in the SSB position.
>>>>>>>>>
>>>>>>>>> 2. One of the grid chokes is open from a tube arc or short.
>>>>>>>>>
>>>>>>>>> 3. If it has always been this way since built the coax cables going
>>>>>>>>> to the input bandswitch may be reversed.
>>>>>>>>>
>>>>>>>>> Input VSWR is a function of plate current & voltage so with one
>>>>>>>>> defective tube it will be quite high and out of the networks tuning
>>>>>>>>> range.
>>>>>>>>>
>>>>>>>>> Dont go ripping things out, that 100W should be more than enough at
>>>>>>>>> 1000W out.
>>>>>>>>>
>>>>>>>>> Also, unless it is a European built/kit amp from Heath UK, or
>>>>>>>>> supplied with a 50 Hz transformer it will have to be run at reduced
>>>>>>>>> power to
>>>>>>>>> keep the transformer from burning up.
>>>>>>>>>
>>>>>>>>> Carl
>>>>>>>>> KM1H
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> ----- Original Message ----- From: "Rahul Sathe" <vu3raz@gmail.com
>>>>>>>>> >
>>>>>>>>> To: <amps@contesting.com>
>>>>>>>>> Sent: Tuesday, September 08, 2009 11:32 AM
>>>>>>>>> Subject: [Amps] SB221 Low Power Help
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Hello Experts,
>>>>>>>>>>
>>>>>>>>>> My name is Rahul call VU3RAZ. This is my first post to the list. I
>>>>>>>>>> am
>>>>>>>>>> seeking help on fixing my old SB221.
>>>>>>>>>>
>>>>>>>>>> as such the amp works on all bands, no arc or parastatics, tuning
>>>>>>>>>> and
>>>>>>>>>> loading is smooth and easy.. I am not able to load the amp to full
>>>>>>>>>> rated
>>>>>>>>>> plate current even with a 100 W drive with my 756 Pro3. Input VSWR
>>>>>>>>>> is high,
>>>>>>>>>> I tried tuning the input tuned circuit but no luck on few bands
>>>>>>>>>> (20, 15).
>>>>>>>>>> With the 756 ATU the things improve but I can not get plate
>>>>>>>>>> current beyond ~
>>>>>>>>>> 400 mA. Even tried disconnecting HT from each tube to see if one
>>>>>>>>>> if the
>>>>>>>>>> 3-500 is dead... both work but even with single tube I am not able
>>>>>>>>>> to load
>>>>>>>>>> the amp fully. Am I looking at dead (weak) tubes ... can both of
>>>>>>>>>> them show
>>>>>>>>>> exact same behavior? Or I am missing something I am not sure if I
>>>>>>>>>> need to re
>>>>>>>>>> build the PSU (replace caps)
>>>>>>>>>>
>>>>>>>>>> Please help...
>>>>>>>>>>
>>>>>>>>>> 73
>>>>>>>>>> DE VU3RAZ
>>>>>>>>>> _______________________________________________
>>>>>>>>>> Amps mailing list
>>>>>>>>>> Amps@contesting.com
>>>>>>>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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