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I've got an SX-650 on the bench and FM is very very weak. The tuning meter swings around a bit. I managed to force a signal through it on the signal generator and tweak the RF alignment a bit. I managed to get the signal meter to deflect a few mm with the strongest signal the sencore could put...

This one had me scratching my head. I just finished restoring a Luxman L-100 and I noticed the bass was being cut when I engaged the tone section. I could even it out by turning the bass up to about 3-4 o'clock. I messed around for almost 2 hours trying to figure out what could be causing this...

I'm rebuilding a pair of these, and both tweeters are blown. Replacement diaphragms are available, but I have a problem. I have no idea if I need the 4 or 8 ohm version. The Ditton 25 uses the HF2000 which exists in both impedances. The only thing I could find is a schematic someone drew up that...

I have this Dynaco ST-70 on the bench. It has suffered a major meltdown. One of the tubes failed, the choke is fried. I've been supplied with the choke. There is a good deal of melted wax that has leaked out of one of the output transformers. But both transformers measure the same with the ohm...

I've got a Marantz 2235B on the bench and the FM stereo comes and goes. It takes a few minutes to kick in when I turn the unit on. It then goes in and out of stereo in roughly equal intervals, maybe around 5-10 minutes? I've changed caps on the IF and MPX boards to rule that out. Poking around...

I'm working on an Eico ST70, and even after doing a full recap and doing some mods it still has a high enough noise floor I can hear it from listening distance. The noise floor does not change with volume. It is a hiss. I replaced all the electrolytic caps, using the multi-can caps from Hayseed...

The variable capacitors in the RF stage in Marantz tuners are sometimes stuck and I currently have no way to get these unstuck without breaking them. Does anyone here have a method? The solder connection between the screw and the orange disk breaks and then I have to try and resolder or glue it.

So I'm a full time tech yet I'm a noob with RtR. But a friend talked me into looking at this machine because there is no other tech around who he trusts to take good care of it. It is spinning way too fast, and it slows right down maybe 1/3 the way into an 8" reel (correction, 7). The speed...

I've got a marantz 1150D here that has a buzz because someone screwed up the original grounding scheme. Figuring out how things were originally wired is always fun times... Does anyone have one on the bench they can take pictures of? Or pictures from a previous project? Particuarly around the...

So this is sort of behaving like a dirty switch issue but thorough cleaning has made little to no difference. And it doesn't quite behave like a cleaning issue. I'm getting popping through the speakers that noticeably moves the woofer. For some inputs, it happens in one channel. For some it...

I'm working on a Dynaco PAS preamp. There's a hum in one channel but I can't quite figure out where it is coming from. The power supply has been replaced with this new board, which is apparently when the problem started. Rail voltage might be higher now, not sure. One schematic I found shows the...

Hoping someone else is familiar with this isse, I haven't seen it before. Seems like a dirty gang, and the contacts were tarnished, but I think I should have made at least some progress cleaning it. I can only sort of get one station, just under 102. Almost comes through in stereo now, and if I...

I'm rebuilding this ST70. I just installed the dynakit bias kit that lets me balance the bias of the power tubes so they don't need to be matched. But I think I had this issue before then too. Hopefully this is a quick one. The bias is a bit too high even when the bias control is at the low...

My guess is they aren't real, but want to see if someone has a definite answer.

I've got a second Marantz on the bench with no FM stereo. Tuner issues are my weak spot. I normally check the 19kHz, but the service manual doesn't show an adjustment or test point for it. Where should I start?

19kHz pilot is set right. I tried a spare multiplex chip. Tried swapping out the two transistors on the MPX board for KSC1845. Freeze spray didn't bring it back. Signal strength seems good. I changed the electrolytics on the MPX and IF boards. Nothing had any effect. What should I try next?

I've made an attempt to fix the notorious Sony hinges. The plastic ones where the spring always breaks out through the back of the plastic. I went to a local plastics store and bought a sheet of 1/8" ABS (might have actually been Kydex). I cut a couple patches to go over the back of the hinge...

I'm trying to align the scope on this 4400 and something other than the adjustments seems to be out of wack. The horizontal alignment is correct but the vertical is way off. I can't get it below the top quarter of the screen. Going by the service manual, there should be no voltage difference...

I just restored/recapped an MC2100 power amp and it still makes a pop through the speakers on powerup. Is that normal for this amp, or is it supposed to have a delay circuit of some sort? Also, I found this service bulletin. I guess I should do this. What modern parts should I use to replace...

https://youtube.com/shorts/0MCyTO6fTmo?feature=share I can't figure out what is causing this. This unit is here for an overhaul. When I adjust the volume, the right channel woofer moves in and out as I turn the control. When I push the mono button, the issue goes to both channels, which should...

I must have done something to cause this but I can't figure out what. And I've never seen an issue like it, and I've restored lots of marantz. There is a low frequency oscillation/motorboating usually in both channels when both L and R phono inputs are shorted. It plays fine otherwise. The...

This is another unit where someone replaced the multi-cap with individual caps stuck to the bottom of the chassis. I have the cap from Hayseed Hamfest. I'm a bit unclear on the wiring, and I'm not 100% sure from the schematic which section of the cap is what value. Does A/B/C correspond to...

I'm working on a pair of ESS AMT1. One cap is a different value in each pair of speakers. It looks like there are a few versions of this crossover and I'm not sure which caps are original so I'm having trouble figuring out what the values are supposed to be. Each speaker has two 100uf caps in...

I'm working on restoring a Marantz Model 15 and it is giving me some grief. I replaced all the caps, and some of the lower value carbon comp resistors. I tested the output transistors on the cricket tester and one of them failed the leakage test. After reading on DIYaudio I'm expecting to have...

A friend recently said he had a receiver he wanted me to look at. I ask him the make and model, he says it is a Zenith MC7041. I think "Zenith, really? Never seen a quality one." But before saying anything I looked up the model and thought, "Oh, that looks half decent." When he brought it I...