RM KL400 problem

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FAFFER
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Re: RM KL400 problem

Post by FAFFER »

I bought some 68 ohm 5 watters from Ebay last week...8 for a fiver.
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Phoenix
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Re: RM KL400 problem

Post by Phoenix »

Cheers can you check with seller if they have 100 ohm thanks
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wa10
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Re: RM KL400 problem

Post by wa10 »

Make sure they are not wirewound resistors, some wirewounds can have enough inductance to effect the feedback loop.
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Re: RM KL400 problem

Post by Phoenix »

Thanks
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speeddemon

Re: RM KL400 problem

Post by speeddemon »

Hi. Dont forget to pickup some hd.Teflon wire n rewind them transformers .. pce n 73'
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Phoenix
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Re: RM KL400 problem

Post by Phoenix »

Hi there can you explain the reasons for teflon and the re-wind thankyou
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Re: RM KL400 problem

Post by speeddemon »

Hi looking at your pic of burnt cap/resistors / and bad transistors. . more than likely wire's in transformers are rf cooked ie shorted out. :ugeek: besides you going to rebuild it its a gd idea to redo transformers anyway's while you at it.pce n 73's
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Re: RM KL400 problem

Post by Phoenix »

Is it just a matter of copying the length of wire and number of turns ? cheers
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Re: RM KL400 problem

Post by speeddemon »

Hi Yes. .. its a gd General rule of thumb to go by ..when you dont have a schematic to go by ..but if you hav right schematic for it id would go by schematic /service manual for correct number of turns to be 110% accurate :ugeek: n cheers n 73's
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Re: RM KL400 problem

Post by Phoenix »

Cheers for that and thanks for the diagrams
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Re: RM KL400 problem

Post by astradyne »

Not sure if it will be of any help, but here are a few snaps of the inside of mine. To my knowledge it hasn't been tampered with.
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Re: RM KL400 problem

Post by wa10 »

Andi, That does not look standard to me,

somebody changed the 10ohm B/E resistors for larger 12ohm tacked on top of board,

modded the bias circuit for some thermal tracking,

power rail decoupling caps have been changed for larger caps,

feedback resistors are typically baked beyond readability & input resistor looks baked.
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Re: RM KL400 problem

Post by astradyne »

wa10 wrote:Andi, That does not look standard to me,

somebody changed the 10ohm B/E resistors for larger 12ohm tacked on top of board,

modded the bias circuit for some thermal tracking,

power rail decoupling caps have been changed for larger caps,

feedback resistors are typically baked beyond readability & input resistor looks baked.
I have no idea Mr. W.

It had intact warranty seals when I purchased it, which I broke to take these pictures. Obviously they can't have been original...

It does sound like some positive mods have been done to this particular amp then? It certainly works very well although the pre-amp isn't the best.

Any ideas on the value of the input resistor? It may look baked but be working fine, but for a few pence it could be worth replacing it.
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Re: RM KL400 problem

Post by wa10 »

The input resistor far left of bottom pic should be 150ohm, the resistor on the opposite side of the power setting board should be 27ohm or 22ohm if it has one,
the large baked feedback resistors should be 68ohm.

most RM amps i have seen have resistors that have been at least slightly smoking, some of them still work with parts that got so hot they dropped out of the board.
W8JI
"An antenna with a poor ground using few radials cannot have a support mast grounded to the radial common point (at least it shouldn't if designed properly) There is no exception to this!
speeddemon

Re: RM KL400 problem

Post by speeddemon »

http://Www.Nteinc.com :ugeek: flameproof resistors :thumbup:
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