Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12) x

Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

Philco 49-607 inop
#46

Consider, at the very least, replacing the caps involved with the audio stages, especially C200, C201, C202 and C204.  In addition, the B+ and Cathode Bypass caps are important.  These are C1000D, C303, C401 thru 403, C405 thru 407.  Failure of any of these caps could cause bias or oscillation issues.

Did you substitute the speaker or merely place it in parallel with the existing speaker?  A speaker with an "off center voice coil will sound "raspy" and will get worse as it gets louder.

I often recommend the installation of an Aux input to increase the usefulness of the radio but also to "divide and conquer" as to whether the issue is with the RF / IF / Detector section or the AF Amp section.  However, I do not usually do this on AC-DC AA5s and especially not on Battery / Line Power portables for 2 reasons:

1. The power output on these portable sets is only about 0.2W
2. This is a "Warm Chassis" set that has a rather high leakage from chassis to ground depending on power
    cord polarity and status of the on-off switch. 

However, temporarily disconnecting the radio signal from the volume control and injecting an audio signal from an external source (MP3 Player on its own batteries would be safest) way to do so.

Attached below is a section of the diagram.  Cut at the "X" and inject at the arrows, with the "hot"(tip) of the output on the pot side of the X and the ground (shield) of the MP3 to the junction of the pot, R201 and R202.  Use an MP3 with an all plastic case or set the MP3 before powering up the radio.

   

Hope this helps.

"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis

Best Regards, 

MrFixr55
#47

I disconnected the speaker wires before connecting the good 8ohm speaker.
I may try to do the test with an external devise to check the amp. If it is still bad I will replace those caps in the audio circuit.
I have other things I'm working on now and also looking for an old belt to repair the handle on this radio. It really looks good since I cleaned it up.
Thanks for all your help.
James
#48

Mrfixr55,
Is the X where I disconnect from the volume control and check marks where the output of the Mp3 goes? Is one the ground wire?
Can I use a cell phone or is there a chance of damaging it? How about a transistor radio? I dont have a MP3.
Thank You
#49

After looking at the schematic closer I understand where to inject the signal. Is it ok to use something other than an MP3 player?
James
#50

One has to be careful when using external signal sources with AC/DC radios.
That is, when using the radio that works off of a battery, it is easier, but when it works off the AC, there are issues of handling the galvanically coupled AC outlet, that could be L or N, to what is being used as the common of your signal.
Again, when your MP3 also works off the battery, it is fine.
So is any source that works of isolated AC/DC power supply. But some Isolated supplies still bring Neutral (that is GND, which is same potential as Neutral) to the Negative of their output, which again could create a problem.

Decoupling through transformer/capacitors helps, especially transformer, as it galvanically de-couples the circuits. Capacitors are a bit more tricky, as they allow current flow and so will allow some undesirable conditions to occur, if not paid attention to.

People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.




Users browsing this thread:
[-]
Recent Posts
Zenith H725
The PSU filter cap arrived today (thank you USPS!) so I will work on that later. Meanwhile, I have the dial, speaker...EdHolland — 06:42 PM
Philco 610B oscillator wiring
Thanks Terry. After checking my notes I think I recorded about -10v at the 6A7 G4/control grid. The screen grid (G3 &...Tubester — 05:59 PM
The list of my radio & TV collection!
Magical chords of forgotten melodies, old nostalgic music on an old radio... Saturday night blues on the Mid-Waves on an...RadioSvit — 12:20 PM
Philco 42-345 Restoration/Repair
Thank you MrFixr55 the issue with this radio is that the internal coil antenna is missing and there was a wire in its pl...osanders0311 — 11:34 AM
Philco 610B oscillator wiring
Regarding the oscillator circuit which is comprised of the 6A7's cathode, control grid, and screen grid. These elements ...Radioroslyn — 10:33 AM
Philco 42-345 Restoration/Repair
Hi OSanders, First off, welcome to the Philco Phorum where Phine Phamily-Phriendly Pholks Phull of Philco Phacts and P...MrFixr55 — 08:41 AM
Philco 42-345 Restoration/Repair
Today I've been reading through the site trying to learn more about this radio. I also soldered the lose power cord cabl...osanders0311 — 08:24 PM
Philco 610B oscillator wiring
Thanks David! I do have that same later prodution model 610 schematic. I've also studied the Philco service bulletins fo...Tubester — 08:12 PM
Philco 610B oscillator wiring
Some info from Beitmans says late production. David   David — 06:06 PM
Restoring Philco 96
Oh wow! Just found this thread.  Brings me back to early days on this phorum.  I did a 96 back in 2017.  Thread here: ...rfeenstra — 06:05 PM

[-]
Who's Online
There are currently 2449 online users. [Complete List]
» 2 Member(s) | 2447 Guest(s)
AvatarAvatar

>