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Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE! |
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13th Apr 2018, 12:45 pm | #1 |
Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,766
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Hacker Hunter RP38A
This radio was a repair I took on from a forum member. As I suspected both the output transistors and let's call it the driver were s/c, the insulation had melted on the outputs, which suggested to me that it had been run on an external power supply.
Having read up on this module I checked all the resistors, most were found to be way out of spec, so I replaced them all including the two pre sets. Also all the transistors were replaced. With a 0 to 10ma meter in circuit, there is a convenient link for this purpose, a tweak on the pre set gave the 3 m/a quoted in the circuit then set the mid point. This has a direct effect on the idle current, but a bit of re tweaking got it spot on. When connecting the amp to the radio I was greeted with a howling noise, not motor boating but a constant tone. I tried all the usual suspects like the five pin plug/socket, re soldered all the earth connections, on off switch high resistance, still the same. I found by reducing the 0.1uf capacitor on the input by half the set worked fine. But I needed to find the cause of the problem, tried linking parts of the print on the audio board, no the fault still persisted. Then I linked the earth on the amp board directly to the chassis of the radio, fault cured. In effect bridging the screen on the screened lead, which of course I had checked for continuity before, so I had spent too long on this at that stage. I soldered the link on the five pin plug, and to the radio chassis. Then I noticed that the slightly noisy amp had gone very quiet. Did the link cure it, don't know, maybe someone who has the same radio would like to try it. Mick. |
26th Apr 2018, 10:09 am | #2 |
Nonode
Join Date: Jan 2004
Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
Posts: 2,967
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Re: Hacker Hunter RP38A
This is a common fault on many Hacker radios.
Below is the link to the write up of my Hacker Hunter TP38A repair which has been working perfectly ever since. I hope you find it helpful. https://www.vintage-radio.net/forum/...d.php?t=111589
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Simon BVWS member |
26th Apr 2018, 10:30 am | #3 |
Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,766
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Re: Hacker Hunter RP38A
Thank's for that Simon ,on my set I tried bridging all the earth paths on the audio board no cracks apparent , the fault persisted ,cleaned the plug /socket and re tension , the fault persisted , the cure was to add a separate earth wire soldered in the plug and onto the chassis of the radio section .
This also seemed to cure the slight rustling noise that was there even at min volume . I left well alone at that stage . Mick. |