>
>On Tue, 2 Dec 1997 22:21:16 -0500 (EST) W2GR@aol.com writes:
>>Hi guys, i've got some amp questions and this seems to be the right
>>place to
>>ask them....Name here is Mike and I've got a line on a Dentron
>>MLA2500B for
>>abt 500 bucks.
>
>A great amp if the tubes are good; make absolutely sure of that first
>since new ones are around $500 each.
It might be a good idea to test the tubes with a high-pot at 5kV. If the
leakage is over 10ua with plus on the anode, reverse the polarity. If
the leakage decreases, the tube has microscopic loose gold melt-balls
inside the envelope. This condition is not necessarily fatal.
>
> This will be my first amp and was wondering how this
>>amp
>>stacks up.
>> It uses a pair of 8875's ..are they still available and how much
>>power can
>>I expect out? Also$$$$$
>
>The amp will do 1800W but for tube longevity keep it in the 1200-1300W
>range.
The max. keydown rating is 700mA for the 8875s.
>Make sure that the grid swamping resistor, R-1, is in the circuit.
R-1 is a wirewound resistor.
>Many MLA owners cut it out to get even more power!
Rogers on that, good buddy.
>> I will be driving it with my 1000MP, will the TR be fast enough?
No
... ...
>> Does it have any protective circuits?
It needs 20 ohms at 20w in series with the B+. If you discover that the
vhf suppressor resistors measure more ohms than 150 ohms ea., it might be
a good idea to improve the suppressors.
>NO and the low speed fan is too slow. Add resistance in parallel on the
>terminal strip to speed it up a bit.
>
>> Can it be used for the WARC bands?
>
>Many will smoke the plate choke on 12M. There appears to be a winding
>difference or tolerance between some MLA's. Try running it at 600W or so
>on 12M then feel the lower end of the choke...AFTER discharging the caps,
>pulling the plug, etc!! If you feel a hot spot, remove 5 turns and try
>again. The trick is to place the choke resonance up in the CB band.
amen, or get a dipmeter and park the choke resonance on Channel 6 before
you give it the smoke test.
Rich..
R. L. Measures, 805-386-3734, AG6K
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