has good strong carrier, autotunes up, but no audio/modulation when using either internal recording chip or external inputs. i see KIA358P Dual opamp in this thing
going to try and replace the dual opamp and also add an ic socket to allow for easy replacement
Not sure if it would cause the same problem in your unit, but the audio path going to the final audio current amplifier feeding the finals gets its audio from a single pathway which comes from the input selector switch to select between internal recorded audio and external.
The external input port, when a 1/8 mini is plugged into it, switches that input from the internal mic/ext mic pathway to the line input pathway, and all end up going through the on-board audio limiter IC near the input ports on the back. From there it feeds over to one of the contacts of the input selector switch. The internal recording audio passes through all the bypassing internal to the external mic and line level input jacks, but is still fed through that limiter IC.
The input selector switch has 3 leads. The one in the center is the one that goes to the audio path leading to the audio current amplifier. It is coupled through a capacitor..C301 I believe.
Anyway you can inject line level audio onto that middle contact wire on the back of the input selector switch and audio will feed directly to the audio current amplifier which feeds the two RF finals. Audio should pass and modulate the carrier if there is nothing wrong with the audio current amplifier circuit.
Unsolder the middle wire from the input selector switch. Couple line level audio to this wire and ground. It should modulate the carrier and produce audio at the receiver.
RFB
i need detailed pics of the talking house II v2 motherboard top and bottom. it's stamped on board as
TH-II-MB
9500TH2101 VER 2 0
also need to know what JP 200, 201, and 202 are for
here is detailed pic's of my board and rear of THII
Lefty Gomez recently bought a TH II. He had similar audio problems. He found a ring crack at the direct input jack. A simple resolder of the connections for the jack took care of the problem.
While your in there, replace C301 with a 1 uf capacitor for MUCH better low end response. See my post about Talking House Simple Mod...
if you look it says c301 but there is no cap or even mounting holes where it says c301. it's right next to the KIA358P dual opamp
C301 can be found by looking at image #2 in your image collection of the unit. Find the op amp IC301, then look to its left. There are two resistors, R301 and R302. Now look directly above those two resistors. There is a canister electrolytic cap and a ceramic cap. The electrolytic canister cap is C301 and the ceramic cap next to it is C337. There is a second canister electrolytic cap to the right of C337, and is labeled as C302.
As to the two open jumper points, JP201 and JP202, those may have to do with the digital audio recording chips (3 of em)...the ISD chips. These would not have anything to do with the finals not getting modulation from the external source as external audio (direct line level) does not pass through the digital recording chips. The AUX input is where you would feed audio to store into these digital recording chips. These are the earlier versions and do not contain very much room for recording and is why the V2 unit has 3 of em compared to the TH V5 which has only one.
Audio goes into pin 6 of the op amp IC301. Run some audio into the unit from the Line Input jack and then go to pin 6 of IC301 and check for audio there. Then check pin 7 for a signal as pin 7 is the output pin for the first half of the op amp being used as the input audio amplifier. If audio is present at these two pins, proceed to pin 1 and check for audio there. This is the chip's second amplifier half output and is what leads to the current amplifier which drives the two finals.
To aid with IC301 and its pinout..here is the datasheet:
http://www.datasheetcatalog.org/datasheet/kec/KIA358P_S_F_FK.pdf
Hope that helps a little.
Oh while thinking about it, I noticed your avatar picture on your image library is of a CCuff C-Quam exciter board. I also noticed an inductor tuning canister at the output. Out of curiosity, what type and value of inductor is that?
RFB
that was chris' 100mW version. it had a larger output coil (my guess some kind of shielded coil) and transistor.
shit!!! got to run back to crap shack. i didn't get a polarized 1uF cap!!!!
"it had a larger output coil (my guess some kind of shielded coil) and transistor."
It appears to be either a shielded local oscillator inductor or an IF adjustment inductor like those used in the front end's of AM radios.
Does it's core have a color and does the slug have a slot in it for using a tuning tool to adjust or is it solid?
RED: local oscillator
YLW: IF bandwidth
BLK: sensitivity
However after market inductors may not have the color indicating what they are meant for.
On the Alfredo "UnLite" units, the ones I have..and the ones with the added power transistor on the final has a molded inductor (520uH) choke for the B+ line feeding the power transistor collector. There is a grain of rice bulb in series with the collector and inductor for current indication and a method of protecting the output transistor from a direct short on the antenna.
My units do not have that shielded canister coil but I have thought about adding one to aid in filtering the output a bit and give that non-tuned output something to bring it in to resonance.
RFB
bad opamp 🙂 replaced with another dual opamp from crap shack
THII v2 repaired and being tested
That's great! Ya sometimes the old rat shack comes in handy...rare but sometimes.
RFB
someone seen my repairs and is swapping me an apsisys cquam tx for the THII. i'm going to muster up some cash and get the thIIv5x (i.AM version) and an external atu. going to put the cquam in a 1ru housing with a 5 watt amp and convert the inputs to balanced 600 ohm. use it for C-C setup
Despite all the nay saying that has been done across several forums about the APSISYS AM C-QUAM unit, they are top notch and exceed FCC 73 specifications. Those guys out there in Greece know their s*i# and manufacture incredibly reliable gear.
I had asked a few of those nay say folks if they even had one on hand to support their stance...not a single one of them had a unit themselves! How ironic. Go which ever direction the prevailing winds are blowing even though that wind is fixing to blow you right off the cliff.
You will get 73 performance out of that APSISYS unit. Tie it into a spectrum analyzer and audio spectrum analyzer and phase analyzer and see AND hear for yourself how good that unit is that everyone "thinks" is worthless....yet those same folks keep buying those Chinese garbage and inferior kit stuff and have closed minds. Go figure.
Enjoy the APSISYS, your gonna wonder why you never had one to start with.
RFB
the apsisys guy has bought all the cquam generators i sold in past years. think i shipped him two or three to him, a Delta, harris, and a couple of BE's
i have heard that he knows his sh$%. i have sen him post in various forums and can tell by his posts he know his sh#$.
i have been trying for a long time to get one of those apsisys tx's.