thanks so much that is really a lot of good information. measured 760R on both channels of the turntable probing from center to shell RCA, so apparently i'm dealing with magnetic turntable. as i mentioned in an earlier post there are no ceramic/magnetic switch or anything that resembles that. only a couple trimmers on the RIAA board itself. inserting a paper clip into the phono inputs as you described unclejed gave a very deep bassy hum, but only on one channel and not very loud. i have verified continuity from the input jacks to the RIAA board.
think my next step will be to pull out and desolder the RIAA board output lines and feed a line level signal toward the source selector in the receiver in place of the signal from the RIAA, see if all plays good then. this will also give the chance to feed the output of the RIAA into a known good set of amplified headphones.
if it is the RIAA, which it probably is, i'll just proto board myself up a new RIAA with a couple of opamps and stick that in. don't even know why i care about fixing it, as all my stuff is on the ipod anyway ... i mean i have like <25 records to my name, but it's just nice sometimes to kick back and listen to a record. little dust pops and all.
think my next step will be to pull out and desolder the RIAA board output lines and feed a line level signal toward the source selector in the receiver in place of the signal from the RIAA, see if all plays good then. this will also give the chance to feed the output of the RIAA into a known good set of amplified headphones.
if it is the RIAA, which it probably is, i'll just proto board myself up a new RIAA with a couple of opamps and stick that in. don't even know why i care about fixing it, as all my stuff is on the ipod anyway ... i mean i have like <25 records to my name, but it's just nice sometimes to kick back and listen to a record. little dust pops and all.
hey guys,
while i was debugging my RIAA situation i discovered something interesting. i pulled the RIAA board out, and found the wires leading to the function selector (rotary switch, old school). fed my ipod into those wires and bingo, sound. connected RIAA to amplified headphones, as well as another receiver, same thing. very weak output, so, dead RIAA board.
the interesting thing i noticed is on the funcition selectior switch. there were two 100R dropping resistors solderd to it in such a way as to when you selected the tape input, you were putting 100R series resistors inline with each positive input. since my tape input was on the weak side i decied to bypass one of the resistor and see if it made a channel louder. sure enough, it did. so with the 100R bypassed (shorted) the signal level is roughly equivilant to the signal level from the built-in FM tuner (which i am sort of using a refrence).
anyone know why those resistors were there? anyone know if im doing a bad thing by bypassing them, even though it makes my tape input behave like a regular tape input instead of a weak one?
thanks.
while i was debugging my RIAA situation i discovered something interesting. i pulled the RIAA board out, and found the wires leading to the function selector (rotary switch, old school). fed my ipod into those wires and bingo, sound. connected RIAA to amplified headphones, as well as another receiver, same thing. very weak output, so, dead RIAA board.
the interesting thing i noticed is on the funcition selectior switch. there were two 100R dropping resistors solderd to it in such a way as to when you selected the tape input, you were putting 100R series resistors inline with each positive input. since my tape input was on the weak side i decied to bypass one of the resistor and see if it made a channel louder. sure enough, it did. so with the 100R bypassed (shorted) the signal level is roughly equivilant to the signal level from the built-in FM tuner (which i am sort of using a refrence).
anyone know why those resistors were there? anyone know if im doing a bad thing by bypassing them, even though it makes my tape input behave like a regular tape input instead of a weak one?
thanks.
can you be more specific what a VSPS is? google gives many many unrelated hits with that single keyword. thanks.
sweet link TY very much. especially since my receiver has a 12V aux supply.
anyone know why those 100Rs where in series with the tape inputs?
thanks.
anyone know why those 100Rs where in series with the tape inputs?
thanks.
many thanks mlloyd, this will be an interesting read especially since this will be my first foray into the RIAA world. i plan to fab a board/circuit with the exact same dimensions as the ond one so its a drop in replacement.
just bumping this up to see if anyone knows why those 100R resistors were switched into series with the tape/aux inputs. phono and tuner inputs were switched straight to the tone controls board without the series resistor.
when i bypassed the resistors on the tape input, the sound level from the tape input became approx the same as from the built in FM tuner, which for me was good because cranking to 3 on FM produced about the same sound level as cranking to 6 or 7 with a CD player.
wondering if 1) anyone know why those resistors were there and 2) ok to bypass them without damaging something. seems to be working good so far, no clouds of smoke yet.
thanks as always.
when i bypassed the resistors on the tape input, the sound level from the tape input became approx the same as from the built in FM tuner, which for me was good because cranking to 3 on FM produced about the same sound level as cranking to 6 or 7 with a CD player.
wondering if 1) anyone know why those resistors were there and 2) ok to bypass them without damaging something. seems to be working good so far, no clouds of smoke yet.
thanks as always.
gain said:
That's 100K not 10K.. They were there to provide attenuation and provide a high input impedance. With most line level sources they should be there to maintain reasonable level matching between internal and external sources.
would it be acceptable to substitute a smaller value resistor? the input was very weak with the 100K fitted. now i have the 100K bypassed completely and feeding my ipod through the input (ipod at approx 1/2 - 2/3 vol). sounds very good.
however when i connected a straight cd player to the same input with the resistor bypassed the sound was slightly distorted and the volume was on a hair trigger, so i need some resistor there, just looking for a compromise between a too week or too strong input.
maybe i'll just fit a pot inside the receiver and set it and forget it. or at least use it to determine the correct series resistance.
opinions?
however when i connected a straight cd player to the same input with the resistor bypassed the sound was slightly distorted and the volume was on a hair trigger, so i need some resistor there, just looking for a compromise between a too week or too strong input.
maybe i'll just fit a pot inside the receiver and set it and forget it. or at least use it to determine the correct series resistance.
opinions?
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