From: wa2ise@cbnewsb.cb.att.com (robert.f.casey) Newsgroups: rec.radio.amateur.misc Subject: TR2400 repair notes, unwanted noise, low RX, display & keyboard Keywords: tr2400 Message-ID: <1991Dec18.174853.23184@cbfsb.att.com> Date: 18 Dec 91 17:48:53 GMT Sender: news@cbfsb.att.com Organization: AT&T Bell Laboratories Lines: 96 The following are several articles crossposted from packet on the TR2400: copied from packet: Msg# TSF Size #Rd Date Time From MsgID To 318 BF 847 0 13-Dec 0440 KD2EJ 28983_WB2QJA INFO@ALLBBS () Sb: TR-2400 NOISE PROBLEMS PERMISSION GRANTED FOR RELAYING AS INDICATED ON KENWOOD BBS. SB-809 TR-2400 Unwanted Noise: Tone or burst at tx 2-13-80 For complaints of a tone burst type noise, or simply a noise, at initial key down, suspect either a broken losse component, or incorrect valued component on the RX TX unit. On the RX TX unit, Q16 emitter, check C82, a 33 uf tantalum cap for broken connection. If you find a 22 uf cap at C82 replace it with a 33 uf cap. JEB/yn (c) 21380TKC ========================================================================= Note: I haven't tried or verified this, proceed at your own risk. WA2ISE copied from packet: Msg# TSF Size #Rd Date Time From MsgID To 317 BF 1183 0 13-Dec 0443 KD2EJ 28984_WB2QJA INFO@ALLBBS () Sb: TR-2400 DISPLAY & KEYBOARD PERMISSION GRANTED FOR RELAYING AS INDICATED ON KENWOOD BBS. SB-810 TR-2400 Display or Keyboard trouble 2-20-80 Display An intermittent or blank digit may be caused by either a broken lead, or intermittently shorting lead on the PLL unit. On the PLL unit, look in the area of Q12, the touchtone generator. Between Q12 and the board edge locate the D1-D4 lines. Inspect this area for either an open (Broken) lead, or shorted (pinched) lead. Repair as necessary, and check lead dress before reassembly. Keyboard An intermittent or inoperative keyboard row or column may be caused by a torn or pinched lead, or a cracked diode. Again, in the area of Q12, inspect the "T" and "Y" lines for shorts or open connections, and inspect diodes D19-D26 for physical breakage. JEB/yn (c) 22080TKC ========================================================================= Note: I haven't tried or verified this, proceed at your own risk. WA2ISE copied from packet: Msg# TSF Size #Rd Date Time From MsgID To 316 BF 1108 0 13-Dec 0446 KD2EJ 28986_WB2QJA INFO@ALLBBS () Sb: TR-2400 RX LOW & DISTORTION PERMISSION GRANTED FOR RELAYING AS INDICATED ON KENWOOD BBS. SB-811 TR-2400 RX low, INtermittent, or distorted 2-20-80 For any of the above complaints, suspect a broken loose component in the RX IF or audio output circuit on the RX TX unit. Simply pull up on the leads and resolder. Adjacent to Q9, the audio output IC, find C49, a 1uf cap. If broken loose from the board, audio output may be down, while current consumption may be up from the normal 30mA to about 100mA due to the audio output amp oscillating. Adjacent to L10, the discriminator, locate C33, a .033uf cap. If this component is broken loose, audio output may be up approximately 6 dB with excessive high frequency audio response. JEB/yn (c) 22080TKC ========================================================================= Note: I haven't tried or verified this, proceed at your own risk. WA2ISE Copied from the QRZ! Windows Ham Radio CDROM