Garey Barrell <[EMAIL PROTECTED]> made an utterence to the drakelist gang ---------------------------------------------------------------------- Greg -
The normal operating position for the RF Gain control is full CW.
It sounds like your receiver has AGC problems. Tubes subbed with known good tubes, especially V1 - V5?
Start by measuring the voltage at TP-1 (top of chassis, just in front of power transformer.) With the RF Gain full CW and the Preselector tuned well away from the band selected on the Bandswitch (detuned), the voltage should measure -1.35V with a Hi-Z meter. Full procedure in Section 6.4.9 of the R-4B manual.
If it doesn't reach -15V at TP-2 (top center of chassis) in Step 4, check the bias supply (8 uF electrolytic in left rear corner under chassis) for ~-80VDC. Unplug tube V9 and recheck. If OK, the problem may be in area of Q4. If OK, problem on AGC-2 line.
Let us know what you find!
73, Garey - K4OAH Atlanta
Drake C-Line Service Manual <http://hr99.home.mindspring.com/R-4C_Servicez/>
Greg wrote:
"Greg" <[EMAIL PROTECTED]> made an utterence to the drakelist gang
----------------------------------------------------------------------
Hi,
I've recently bought another T-4XC (already had one) , and a R-4B.
I've fixed the R4B , chaged caps, restored switches, replaced the rca ant.connector with a UHF connector, fixed some old bag solder points, replaced the old coaxes
with new ones,and now the receiver works...
However I'm wondering if there are any performance tweaks for it, I've checked
http://www.mods.dk/print.php?ArticleId=2549 but surely there must be more fixes out there? It's already modified a bit and since it's not 100% original anymore
I might as well tweak it some more.
I also have a question about the RF Gain adjustment, exactly how is it supposed to
function? Positioning it first half of the scale the radion is totally dead, no audio at all,
around 3/4 of the scale it starts to receive, cranking it up to near max the audio starts
clipping and it sounds awful...
Are there any testpoints for voltages / bias to check etc?
//Greg
----------------------------------------------------------------------
On Behalf of "Greg" <[EMAIL PROTECTED]>
Submissions: [email protected]
Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body
Hopelessly Lost: [EMAIL PROTECTED] - help in body of message
Zerobeat Web Page: http://www.zerobeat.net
Brought to you courtesy of TLCHost.net http://www.tlchost.net/
----------------------------------------------------------------------
---------------------------------------------------------------------- On Behalf of Garey Barrell <[EMAIL PROTECTED]> Submissions: [email protected] Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Zerobeat Web Page: http://www.zerobeat.net Brought to you courtesy of TLCHost.net http://www.tlchost.net/ ----------------------------------------------------------------------
