>
>> I understand that the AL-1500 has a grid-trip circuit. The 8877 (s/n
>> HSZ501)I tested this morning had gold-sputtering. It was removed from an
>> AL-1500.
>
>Alas, the grid-trip circuit in the AL-1500 limits at a whopping 175ma Ig, and
>is not adjustable.
>
That works out to be c. 8w dissipation. According to my spec sheet, the
grid will safely dissipate 25w.
>> >An 8877 has no business having over 75 ma grid current flowing for any
>> >reason.
>>
>> Only c. 5W?
>
>At 2250 watts output, an 8877 draws less than 65 ma grid current.
>75 ma limiting is plenty of headroom. A cap sits in the base circuit
>of the TIP120 to prevent nuisence trips.
>
>> >8877's are $700 + per pop (pun intended) now from RF Parts. The above is
>> >really
>> >cheap insurance. Works good, lasts a long time.
>> >
>> Ever ran an 8877 with no suppressor whatsoever?
>
>I have not personally, but if you look at old Orr and ARRL Handbooks,
>you will see several 8877 projects sans the Supp.
>
For VHF applications, surely.
cheers, Phil
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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