Sruddy's FM-200-B Restoration Thread
- Thread starter sruddy
- Start date
For anyone wanting to experiment with different colors you can use a marker to draw the tint right onto the lamps glass tube. When I first purchased the white LED lamps I used a fluorescent orange marker to warm it up. Now it looks identical to the warm white LED I purchased later. I have also used flash gels to change LED color.
I received the rebuild parts from Jim today and replaced the rectifier, filter can, and line caps. I guess the biggest concern is my voltage readings at all 4 stages of the filter capacitor are higher than spec.. Here are my readings before and after the power section restore.
I tried a 100 ohm resistor before C28A and it only knocked things back by 10V. Should I be worried about the out of spec voltage?
The other thing is I received snubber caps were I was going to install XY safety caps. I went ahead and installed them but don't know why yet.
- C28A - spec 225V - before 229V after 262V
- C28B - spec 200V- before 223V after 255V
- C28C - spec 175V - before 216V after 247V
- C28D - spec 148V - before 208V after 237V
I tried a 100 ohm resistor before C28A and it only knocked things back by 10V. Should I be worried about the out of spec voltage?
The other thing is I received snubber caps were I was going to install XY safety caps. I went ahead and installed them but don't know why yet.
LOL feel like an idiot it's so elementary!!
New issue, put all tubes in and all sections test just about 10% above spec so I think I'm fine. However after trying it out I only have one channel of output. Well correction, the bad channel can be heard if I turn the balance all to it. Even then you can barely hear it. It does get louder with the tuner volume but not much. I tested V10 and V11 and all four voltages listed in the schematic checked out. What would be the next think to check?
Typically, all the voltages indicated are with no antenna connected, and no station tuned in. That makes a difference as well, versus receiving a station. The latter scenario will produce higher voltages throughout the tuner.
If the one channel is dead even with the tuner set to Mono, then look at the wiring around the 12AT7 output tube serving the defective channel. If there is sound in both channels in mono mode but not in stereo, the the MPX chassis would be the next target.
Dave
If the one channel is dead even with the tuner set to Mono, then look at the wiring around the 12AT7 output tube serving the defective channel. If there is sound in both channels in mono mode but not in stereo, the the MPX chassis would be the next target.
Dave
When tuner set to mono there is no sound at all. I'll check the wiring again.
update: Channel fixed but mono still out.
Both channels work! Unfortunately I'm not exactly sure what I did to fix it. After checking the voltages at V10/11 and not finding anything out of spec I looked at all the wires going there and traced a few to the volume. I noticed that the volume had a double pot so I assume one was for each channel. After testing the pot, both sections preformed equally, so I ruled that out. I was stumped so I decided to change all the resistors you supplied since they were all associated with the V10/11 sockets. Right after the replacements were finished I noticed a solder drip from the terminal strip right at the right channel output. It may not have been touching the chassis but if not it was very very close so I took that off. Anyway both channels work so I will move onto the rest of the audio coupling caps. There is a bit of intermittent static coming from the left channel so hopefully my parts replacements will clean that up.
But there is no Mono right now, not via either auto or mono on the switch. I have a mono station down the street and the meter is pegged but no audio.
Both channels work! Unfortunately I'm not exactly sure what I did to fix it. After checking the voltages at V10/11 and not finding anything out of spec I looked at all the wires going there and traced a few to the volume. I noticed that the volume had a double pot so I assume one was for each channel. After testing the pot, both sections preformed equally, so I ruled that out. I was stumped so I decided to change all the resistors you supplied since they were all associated with the V10/11 sockets. Right after the replacements were finished I noticed a solder drip from the terminal strip right at the right channel output. It may not have been touching the chassis but if not it was very very close so I took that off. Anyway both channels work so I will move onto the rest of the audio coupling caps. There is a bit of intermittent static coming from the left channel so hopefully my parts replacements will clean that up.
But there is no Mono right now, not via either auto or mono on the switch. I have a mono station down the street and the meter is pegged but no audio.
Do you know if your unit uses the diode matrix switching board for the Stereo Automatic function, or the large, multi-pole relay to accomplish the audio switching? Both the newer and older versions use a relay, but the relay for the newer version is much smaller and simpler than that used in the older version.
If yours uses the relay for audio switching, the first thing is to clean all the contacts to make sure they are not the issue.........
Dave
If yours uses the relay for audio switching, the first thing is to clean all the contacts to make sure they are not the issue.........
Dave
Mine is an early version. I'll check the relay when I get home, thanks.
Mono is working now in both switch positions,Mono, and Stereo-Mono Automatic. There was no mono sound either way yesterday. I replaced the following but don't have a clue as to which part or parts contributed to the fix.
C222,C222,,C85,C86,C17,C41,C59,C73,C81,and C87
I'm getting intermittent static in the left channel. Not very often but it does come and go.I have a few tuners now and this one seems to blow them all away in reception. I notice a swirling high frequency back ground static in my other tuners but this one seems dead silent! I have only listened to it for a short time so I may update my opinion later. Now deciding if I want to add the rest of the parts and get it aligned. It doesn't seem to need an alignment yet.
C222,C222,,C85,C86,C17,C41,C59,C73,C81,and C87
I'm getting intermittent static in the left channel. Not very often but it does come and go.I have a few tuners now and this one seems to blow them all away in reception. I notice a swirling high frequency back ground static in my other tuners but this one seems dead silent! I have only listened to it for a short time so I may update my opinion later. Now deciding if I want to add the rest of the parts and get it aligned. It doesn't seem to need an alignment yet.
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Clean the contacts on the relay. Both stereo and mono audio signals pass through those relay contacts. Dirty ones will cause anything from static, to no signal at all, to anything in between, and all in intermittent fashion......
Dave
Dave
Will do Dave.
I cleaned the contacts on both relays. I also replaced the following C11,60,61,210,and 214. I still have the static mostly during warm up and now it won't go into AFC. It went to AFC fine before my last work. I hope the static isn't an if transformer.
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It does look to have the K-trans units, which seem most prone to the silver mica problems. If thats what it is, they are fixable. The usual method is to open them, gut the internal SM caps, and solder new ones to the bottom side. It requires a re-alignment though.
If the static is only in one channel, it cannot be an IF transformer. Is the static there whether it is operating in mono or stereo mode? If it's there in mono mode, then either the relay, or the left channel audio amplifier circuits should be checked. If only in stereo mode, then either the relay (again) or the MPX circuits are suspect.
In what way is the AFC not working? Does the Microtune no longer work? The front panel lamp not light? Or does it no longer draw an off-tuned station in anymore?
Dave
In what way is the AFC not working? Does the Microtune no longer work? The front panel lamp not light? Or does it no longer draw an off-tuned station in anymore?
Dave
Yes static is only in left channel. When first turning on it is actually a squeally metallic sound. It mostly goes away after a short while but I will get slight intermitent staic during use. If I turn it off and back on the squeally static will always come back for a few moments even if warm. It's in stereo and mono. fwiw I haven't been able to test the nuvistors.
Before the last work the AFC light would be on most of the time, now it's off. It does come on when first powering up if unit is cold and will stay on for a moment on a very strong station. Soon after warm up I haven't seen it come on at all even if I turn it of and right back on. Three of the caps I just replaced are in the RF path so I wonder if one of those screwed up the AFC? Also The kit replaced two ceramic caps C60,61 with PP caps is that ok?