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G8MNY > TECH 27.08.10 07:15l 72 Lines 2788 Bytes #999 (0) @ WW
BID : 60696_GB7CIP
Read: GUEST
Subj: PULSTAR AT1500 ATU
Path: IZ3LSV<IK2XDE<ON4HU<IW0QNL<VE2PKT<ZL2BAU<N4JOA<GB7CIP
Sent: 100827/0125Z @:GB7CIP.#32.GBR.EU #:60696 [Caterham] $:60696_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (New Aug 10)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
This large 1500W QRO ATU flashed over & caught fire, due to poor design of the
roller coaster coil mounting brackets, flammable construction board &
inexperienced user (me) when tuning up with only 400 Watts.
_ _ INTERNAL LAYOUT SIMPLIFIED CIRCUIT
ÚÁÄÁÂÄÁÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ Direct Via
³ S ³ v Fire ³ o Thu ATU
³ W ³ ÜÜÜÜÜÜÜÜܳ TxÄSWRÄ>o Coax1 o<ÄÄ¿
³ R ³ C1 C2 Þðððððððݳ o Coax2 o ³
³~~~ ======= ======= Þðð L ððݳ Wire o ³
³ ======= ======= Þðððððððݳ Via o¿ ³
³ SW ======= ======= Þðððððððݳ ³ HOT ³
³ ÜÜÜ ======= ======= Þðððððððݳ ATU ÀÄ´ÃÄÄÂÄÄ´ÃÄÄÙ
³ º ======= ======= Þðððððððݳ C1 ³ C2
³ º ======= ======= Þðððððððݳ L<¿
³ º ======= ======= ßßßßßßßßß³ ³ ³
³ º º º º ³ ÄÄÄÄÄÄÄÄÄÄÄÄÁÄÁÄÄÄÄÂÄÄÄÄÄ
ÀÄÄ×ÄÄÄÄÄÄ×ÄÄÄÄÄÄÄ×ÄÄÄÄÄÄÄÄ×ÄÄÄÄÙ ///
ßßß ßßßßß ßßßßß Þßß
On the lower 2 back coil insulator combs, there are 2 right angle brackets
that have sharp corners mounted only a few mm away from earth & the RF HOT top
of the tuned circuit high voltage point. They are mounted on inflammable thick
fibre board.
ROLLER COASTER
Flammable³ ³ RF³³³³³³³³³³³Silver Plated
Fibre ³ ³ HOT³³³³³³³³³³³Flat Coil Spiral
Board ³ ³ END³³³³³³³³³³³
³ CDDDDAAAAAAAAAAAFlammable
"L" ³ ³_ø_ø___________Support
Bracket ³ ÇÄÄÄÄÂÂÂÂÂÂÂÂÂÂÂ Combs
Screws (³ º] ^Sparks
³ º___/ Jump Earth
ÄÄÄÄÄÄÄÄÄÁÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄChassis
The Caps C1 & C2 are designed for very high voltage & should be the first thing
that arcs over not these brackets!
REPAIR.
The burnt fibre board & shaped mounting comb strip must be cleaned of any
charred material with a sharp knife. This may mean removal & disassemble of the
roller coaster.
MODIFICATION
To stop reoccurrence of the RF flashover, the 2 RF hot end "L" shaped brackets
were cut down in length & 1 nut & bolt left out of each.
__ ___ __ __ __
Screw³ ³ \shortened
holes
³ ORIGINAL ³ MODIFIED
Doing this mod, adds about 1cm to the flashover arc distance! And has no effect
on the sturdiness of the roller coaster assembly.
LOOSE SCREWS
As this unit has been used for /P work, some screw had soon rattled lose,
despite locking washer nuts! These have been tightened up & threads painted.
Why don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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