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G8MNY > TECH 06.04.06 19:21l 207 Lines 10789 Bytes #999 (0) @ WW BID : 24721_GB7CIP Read: OE5RCO DL1LCA GUEST Subj: Watson 'Hunter' Counter Mods Path: DB0FHN<DB0RGB<DB0MRW<DK0WUE<SP7MGD<IW0GPS<IW8PGT<ON0AR<GB7CIP Sent: 060406/1025Z @:GB7CIP.#32.GBR.EU #:24721 [Caterham] $:24721_GB7CIP From: G8MNY@GB7CIP.#32.GBR.EU To : TECH@WW By G8MNY (New Apr 06) (8 Bit ASCII Graphics use code page 437 or 850) I have bought a damaged one of these small handheld counters, & I went about repairing & upgrading it as there were a lot of components & switch options missing on this bottom of the range model. MODIFICATIONS DONE 1/ Add UHF clipping diodes across the BNC socket. 2/ Stop LCD rubbing marks from the lens casing. 3/ Add bargraph signal meter. 4/ Add gate time push button, to give 0.1s 2s 1s & 5s gate times. 5/ Add low battery indicator. 6/ Add "no prescaler" RF path to read 1 - 30MHz. With 4 & 6 you can read 1MHz - 30MHz down to 0.1Hz & 30MHz - 3GHz down to 10Hz. But calibrating the crystal osc to high accuracy even short term is not easy. There is only 2 other features according to the LCD graphics.. a) swictable filter, & b) a period timer. I did not understand the wiring for a) & I don't think te PCB supports b). Be warned it as all very small Surface Mounted Devices! So other than the I/P clipper protection & LCD case modifications, I do not recommend the other modifications unless you are fairly competent with soldering SMD components on a busy SMD board! O R I G I N A L M O D I F I E D .³~~³. DC .³~~³. DC ÚÄÄÁÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ÚÄÄÁÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ ³ ³ ³ ³ ³ ³ ³ ³ WATSON Hunter o ³ ³ WATSON Hunter o ³ ³-----------------------------------³ ³-----------------------------------³ ³| Frequency PRESCALE HOLD |³ ³| Frequency PRESCALE HOLD |³ ³| MHz|³ ³| MHz|³ ³|[] [] [] [] [] [] [] [] [] [] |³ ³|[] [] [] [] [] [] [] [] [] [] |³ ³|[].[].[].[].[].[].[].[].[].[]. |³ ³|[].[].[].[].[].[].[].[].[].[]. |³ ³| |³ ³| _ - = ð ~ ÚÄ¿|³ ³| |³ ³| signal _ - ð ~ ð ð ð ð ð ³X³|³ ³| |³ ³| _ - = ð ~ ð ð ð ð ð ð ð ð ð ÀÄÙ|³ ³-----------------------------------³ ³-----------------------------------³ ³ 10MHz-3GHz/50ê Frequency Counter ³ ³ 1 MHz-3GHz/50ê Frequency Counter ³ ³ Power Cal³ ³ Power Pre Cal³ ³ On Hold 0³ ³ On Scale Hold Time 0³ ³ [] ³__³ ³ ³ [] [] ³__³ ³__³ ³ ³ ³ ³ ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ \³/___ ____ ___ _______ ___ \³/___ ___ ____ ___ _________ ___ À´PreÃ´ö100Ã´ ö8Ã´CounterÃ´LCD³ À´LimÃ´Pre³ o´ö100´o ³ ö8Ã´ Counter Ã´LCD³ ÀÄÄÄÙÀÄÄÄÄÙ³ö16³ÀÄÄÄÂÄÄÄÙÀÄÄÄÙ ÀÄÄÄÙÀÄÂÄÙ\oÀÄÄÄÄÙo/³ö16³ÀÂÄÂÄÄÂÄÄÂÙÀÄÄÄÙ ÀÄÄÄÙ Hold ÚÄÁÄ¿ ³ÚÄÄÄ¿ ³ ÀÄÄÄÙ ³ ³ Batt³ ³Det³ À´AmpÃÄÙ ³Hold Time ÀÄÂÄÙ ÀÄÄÄÙ ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ FRONT END FAULT The fault was a blown up front end SMD MIMIC (A06), as there is NO input protection fitted! As I could not find a replacement device to hand, I used a scrap cellphone preamp SMD NPN & made up an amp with just an additional bias R (22K). This NPN fitted over the 4 pad AO6 OK, with the bias SMD 22K (selected to give the same current as the 2nd A06 stage) & placed over the NPN. It all worked well & a QRP 2400MHz Tx was measured OK with the search aerial alongside. ORIGINAL REPAIRED ÚÄ´ÃÄÄÄÂÄÄ+5v ÚÄÄ´ÃÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄ+5v ³ 100 °° °° ³ 100 °° °° ³ ³ In Gnd ³ ÚÄ22KÄÅÄ´ÃÄ>U2 B unused (o)Ä´ÃÄ´>ÁÄ´ÃÄ>U2 (o)ÄÄÂÄÄÄÂÄ´ÃÁÄÄÄ´< BNC³ U1º Gnd Out ³ _³_ _³_ e³ E C ³ º °° °° ³ \_/ /_\ ³ °° °° ÀÄÄÄÄÄÐÄÄÄÄÄ PCB PADS ÀÄÄÁÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄ PCB PADS 1/ To reduce the chance of a re-occurrence I added 2 UHF clipping diodes wired across the BNC socket. 1N4148 diodes will do if you have no better. 2/ I had heard of someone breaking the display, this makes the unit a total write off! Looking at my display, I could see tell tail marks (lines) where the LCD had been rubbed by the sharp case lens metal stamping edge. _P_L_A_S_I_C__L_E_N_S_ ==========<______________________>============ Embossed`=======ð ð==' Metal Case ^sharp edges^ °°°°°°°°°°°°°°°°°LCD ________________³__________XTAL_³__________PCB To remove the sharp edges, use a small modelling knife held parallel to the case so that the lens can't be damaged. Then firmly drag the blade over the raised edges, scraping off the sharpest part of the edge. Go all around the raised lens stamping edge, make sure that there are no proud part that could put concentrated pressure onto the glass LCD. (eg. when dropped) 3/ To make the bargraph display work add a uhf diode to half of D2. I used a schottky one across just 2 of the 3 SMD diode pads. Note DIODE Polarity! Also add a 1n instead of adjacnet missing R. ÄÄÄÂÄÄ+5v °°Ä¿ U2 100 _³_ Ä´ÃÄÂÄ´>ÄÁÄÄ´ÃÄ>U3 Prescaler °° D2 /_\ _³_ ³ /_\D2 oÄÄÄÄÂÄÄÄ°°ÄÙ ÀÄÄÄÂÄÄÄ>U9 IC °° PCB PADS ===1n 1nÄÁÄ Á ÄÂÄ °° 3/ By moving the HOLD push button from mounting holes "SW6" to the left overlapping "SW4" holes, there is then room to fit an identical button in "SW7" position. ( ( () ) () ) SW4SW5 SW6 SW7 Then you can get the counter to change the gate time from the default 0.2S to the 3 others possible times & hence the display resolution. Then you have to file the existing case button hole to a long slot. This is quite simple to do with a set of sharp needle files, but time consuming! I then cut & filed an ally blank to between the buttons & glued that in place. 4/ This needs 1 small preset pot, 1 SMD NPN (L-4), 2 SMD Rs, & a zener. Looking at the circuit I found the zener needs a series R to work properly, & I selected one on test to make my pot have useful setting range. _____ SW2 D1 +5V <ÄÂÄÄÄÂÄÄ´78l05ÃÄÄÄÄÄÂÄÄÄÄÄo\ÄÄÂÄ´<ÃÄÄÄo+ 9-12v ³ ³ ³ U10 ³ 100K X ÚÄv_Û ³ 10K ÀÄÄÂÄÄÙ ZD1_³_ +_³_ ³ ³Switched ³ R32 ³ 2.7V/_\' _Ü_ ³ ³Power U9<ÄÄ)ÄÄÄ´ ³ ³ Ü ³ ³Jack ³ ³ ³ R31 ³ ³ ³ ³ ³ Q7>ÃÄÄÄ)ÄÄ10KÄÄÄ´ X ³ ³ ³ ³e ³ ³ ÃÄÄÄÙ ³ C1=== ³ ³ VR1 R2 ³ 100u³ ³ ³ 22K 56 ³ ÄÁÄÄÄÁÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÙ The battery does not give > 5V, so the regulator is not actually regulating when on battery supply! I suspect there should be more than 4 AA cells (but no room) if the supply needed to be properly regulated for more accurate work! The counter is actually quite accurate for its simple uncompensated xtal system. There a danger if connecting the counter to an earthed supply while having the BNC connected to other earthed kit. This is because the nicad battery charging is via a negative change power switch arrangement. During insertion the 12v will be placed across the 5V battery until the switch breaks the negative battery lead. This may only last a very short time but currents >5A can flow & could damage leads, PCB track & eventually the battery! (good for battery for a few seconds) BNC DC .³~~³. ÚÄÂÄÂÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÁÄÄÁÂÄÄÂÄ¿ ³o³ ³ ³ VR1 ____ ³____³ ³o³ U1 & U2 I/P Preamps ³~ ³ ³ ³ U7 ³ U1 ~³ ³ ÀÄÄÙ ÀÄÄÄÄÙ ³ U3 3GHz ö100 Prescaler ³ D2 U2 ³ ³ ³ U4 & Q3 No Prescaler bypass amps ³ ÚÄÄÄÄÄÄÄÄ¿ ____ __ ³ ³ ³ ³ ³ U6 ³ U4 ;³U3³:³ U5 Gated ö8 & ö16 prescaler ³ ³ U9 ³ ÀÄÄÄÄÙ 'ÀÄÄÙ'³ ³ ³ ³ Q2 ³ U6 Overflow Counter decoder ³ ÀÄÄÄÄÄÄÄÄÙ ÃÁÁÁÁÁ´ Q1 ³ ³ X1 ³ U5 ³ _ ³ U7 Gate pulse counter ³ Q7 TTTTTTT :³_³]³ ³ U10 ³ U9 Counter IC & display driver ³ ___³ ³ Batt³___³ U10 5V regulator ³_ _³ ³o³ ³o³ X1 4.19407MHz Crystal ÀÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÙ 5/ A far more complex modification is to add the 2 HF amplifiers, missing for the no prescaler mode, & move/add switches to control it. +5vÄÄÄÄÂ 7,3,2ÚÄÄÄÄÄÂÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ 100 ÚÄÄÄÁÄÄÄ¿100 6K2 ____ ³ ÄÄ´>ÄÅÄÄ´ÃÂÄÄ´U3 ö100ÃÄÁÄ´ÃÄÁÄ´< Q1 ÃÄ330Ä)ÄÄÄÄÂÄ+5v U2º ³ ³ 1ÀÄÄÄÂÄÄÄÙ4 e³ ³ o ³ oÄÄÄ>U9 Ð ³ 100K 5³7 Á ³ o <ÄÄÙSW3ÚÄÄ>o ³ Á Á ÚÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄ)ÄÄÄÄÄÙ Á ³ R13 R14 ³ 1,7,9ÚÄÄ+5v R ÚÄÄÄÄ¿ 310 100K ____³ ÚÄÄÄÄÄÁÄ¿11 2K2 100K ÃÄÄÁÄÄ´ÃÄÁÄÄÄ´< Q3 ÀÄ´ U5 ö8 ÃÄÄÄ>IC U9 ÀÄÄÄ´ÃÄÁÄÄ´< C12 e³ 2³ ö16 ÃÄÄÄ>COUNTER C9 U4 ³e Á ÀÂÄÄÄÄÄÄÙ12 Á Á3,4,5,6 Again instead of a mimic amp U4 I used a biased HF NPN (L-4). But I found that I had to add a series R of 2K2 to C9 so that it did not load U2's O/P to prescaler IC U3. I re-used the changeover power switch SW2, as the SW3 changeover & I found a smaller make switch for the SW2 power switch. Again I had to make new hole for SW3, & I drilled then filed a matching rectangular hole. N.B. Below 1MHz the counter software stops the display from counting. Why Don't U send an interesting bul? 73 De John, G8MNY @ GB7CIP
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