2238 seems excessively "bass-y".......

[adamp]

OK; a bit of background here. I know I'm not just being crazy as I've listened to three 2238's in the past week.

One belongs to a friend, her mom gave it to her as it wasn't being used, and it's currently at my house for a cleaning/relamping which I finished earlier this week but she hasn't come to pick it up yet. It's cosmetically a little rough, but sounds awesome.

I also bought a 2238 last Saturday, it needed a good cleaning, a needle light and a stereo indicator light. Got that one all sorted out and it also sounded great (like my friend's receiver). I had planned to replace a 2220B with this receiver, and I have the 2220B listed for sale, but a guy who came to look at it ended up talking me into selling him the 2238. Back to square one....

Another 2238 popped up in my local classified ads, so I picked it up. It was tough to audition as the speakers that the seller had didn't sound great, and a lot of the switches and pots were dirty. Anyway, it's in cosmetically excellent condition, and functions 100% but doesn't "sound" like my other Marantz receivers (and certainly not like the other two 2238's). It seems a lot heavier on the low-frequency tones than the other two. Like, it sounds like the bass knob is turned to about the 2-3 o'clock position. For normal listening I had the bass knob turned down two notches and the midrange knob turned down one notch (from flat).

This occurs on all sources (I've used FM, iPhone, CD player and a turntable), on both channels and all the time. Any ideas what I should be looking at? I had a quick (visual) look inside again, and I don't see any glaring issues like bulging/leaking caps or anything along those lines.

As a random side note, the 2238 I sold was built March 17, 1977, and the one I just bought was built March 16, 1977. I am going to try and contact the buyer of the "St Patty's Day receiver" and find out what the serial number is, as I'm curious how many off of my new one it will be. Does anyone know how many of a given model they built in a day at that time?

Thanks for any input,

Adam

 

[wurlyman]

OK; a bit of background here. I know I'm not just being crazy as I've listened to three 2238's in the past week.

One belongs to a friend, her mom gave it to her as it wasn't being used, and it's currently at my house for a cleaning/relamping which I finished earlier this week but she hasn't come to pick it up yet. It's cosmetically a little rough, but sounds awesome.

I also bought a 2238 last Saturday, it needed a good cleaning, a needle light and a stereo indicator light. Got that one all sorted out and it also sounded great (like my friend's receiver). I had planned to replace a 2220B with this receiver, and I have the 2220B listed for sale, but a guy who came to look at it ended up talking me into selling him the 2238. Back to square one....

Another 2238 popped up in my local classified ads, so I picked it up. It was tough to audition as the speakers that the seller had didn't sound great, and a lot of the switches and pots were dirty. Anyway, it's in cosmetically excellent condition, and functions 100% but doesn't "sound" like my other Marantz receivers (and certainly not like the other two 2238's). It seems a lot heavier on the low-frequency tones than the other two. Like, it sounds like the bass knob is turned to about the 2-3 o'clock position. For normal listening I had the bass knob turned down two notches and the midrange knob turned down one notch (from flat).

This occurs on all sources (I've used FM, iPhone, CD player and a turntable), on both channels and all the time. Any ideas what I should be looking at? I had a quick (visual) look inside again, and I don't see any glaring issues like bulging/leaking caps or anything along those lines.

As a random side note, the 2238 I sold was built March 17, 1977, and the one I just bought was built March 16, 1977. I am going to try and contact the buyer of the "St Patty's Day receiver" and find out what the serial number is, as I'm curious how many off of my new one it will be. Does anyone know how many of a given model they built in a day at that time?

Thanks for any input,

Adam

Has it been re-capped or upgraded at all or have you not gotten that far into it?

 

[adamp]

I haven't done anything to it, and a quick peek inside reveals that it appears to be pretty untouched since it left the factory.

Adam

 

[adamp]

I did a little digging today. I figure the issue with this is likely on one of the boards that is common to both channels since my issue is present on all functions and channels.

Starting with the P800 power supply board, attached are two pics of the boards from the two 2238's that I still have in my posession (built approx. 3 months apart from one another). The problematic receiver is the cleaner looking board and the filthy/dirty one is the one that sounds good. On both boards, C803 is listed in the parts list as being 470uf 50V but a 470uf 63V cap is present (I realize that this on its own is not a problem, I just thought it was odd). One of the caps on the "good" board is a grey coloured Elna, but the other one is not. The Elna looks factory and is glued on. I suspect Marantz could have used caps from a number of different suppliers, so I'm not super worried about the difference.

C802 and C803 are all identical caps on both boards; same maker and everything, but the shrink tubing on the ones on the "bad" amp don't seem to wrap around the ends of the caps, could this be an indication of swelling/bulging or likely just production run differences? They're the two largest caps on the board, since I didn't photograph it in such a way that the labels are visible.

Should I start with a recap of the P/S board, reset the voltage, set the bias and try it again?

Adam

 

[wurlyman]

I did a little digging today. I figure the issue with this is likely on one of the boards that is common to both channels since my issue is present on all functions and channels.

Starting with the P800 power supply board, attached are two pics of the boards from the two 2238's that I still have in my posession (built approx. 3 months apart from one another). The problematic receiver is the cleaner looking board and the filthy/dirty one is the one that sounds good. On both boards, C803 is listed in the parts list as being 470uf 50V but a 470uf 63V cap is present (I realize that this on its own is not a problem, I just thought it was odd). One of the caps on the "good" board is a grey coloured Elna, but the other one is not. The Elna looks factory and is glued on. I suspect Marantz could have used caps from a number of different suppliers, so I'm not super worried about the difference.

C802 and C803 are all identical caps on both boards; same maker and everything, but the shrink tubing on the ones on the "bad" amp don't seem to wrap around the ends of the caps, could this be an indication of swelling/bulging or likely just production run differences? They're the two largest caps on the board, since I didn't photograph it in such a way that the labels are visible.

Should I start with a recap of the P/S board, reset the voltage, set the bias and try it again?

Adam

I think that's where I'd start. Don't change the value of any caps but it doesn't hurt to go up to the next available voltage. ie: 10 to 16v, 16 to 25v, 50 to 63v, it could make the unit run cooler. I would use Nichicon or Panasonic rated at 105 degrees Celsius. Mouser Electronics is the first choice source. Take your time and be patient. Good luck!

 

[rBuckner]

Does the Loudness button make a difference when pressed? If not, it may just be stuck on. Failing audio coupling electrolytics can also cause that bloated bassy sound. I agree with you and Wurly, start at the power supply to have a good solid base.

 

[ConradH]

Don't know if you have anything to test with, but general advice is never re-cap or do anything else until you troubleshoot the problem and fix it. If power supply voltages are correct and you don't hear hum, there's likely nothing wrong with the power supply. Does it have pre-out and pwr-in? Can you test each section through another unit to see where the bassiness comes from? Definitely do DeoxIT the switches, especially loudness and any filters.

 

[adamp]

Thanks for the replies, guys....

I hadn't thought of using the pre-out/main in jacks, I'm a bit of a hoarder and definitely could have isolated the pre and power amp sections.

The loudness button works, and I guess I forgot to mention that I already deoxit-ed all the controls and replaced the stereo indicator bulb.

At any rate, I was off work yesterday so I acquired the six electrolytic caps on the PS board locally, replaced them, and tried it. It still sounded pretty bass-heavy, but a little more crisp and less muddy if that makes sense?

You know those guys who you lend a tool to and it takes them months to give it back? A buddy had borrowed my DVOM to troubleshoot some electrical woes on his car, literally for months. Anyway I got it back from him today, adjusted the power supply voltage (it was close, 35.4V), and performed the "power amp setup" procedure from the manual? The 14mV spec (bias?) measured low, about 8-10mV on both channels, and the 0mV spec (idle?) was about 10mV before adjustment.

Anyway, after doing all that, it seems to be sounding like the other 2238's; it's currently playing side 4 of Pink Floyd's "The Division Bell" through a pair of Wharfedale 420s and sounds great! I think I prefer my Dynaco A35's though... And also, it being after midnight, I can't really crank it up to see how it performs at higher output levels... Will have to check that tomorrow after work so as to not drive the neighbors insane. I'll report back but it's definitely pretty vastly improved from what I can tell.

Thanks for the advice,

Adam

 

[rBuckner]

Honestly, those adjustments weren't that far off to cause any issues and not the heavy bass I would think. I'm afraid the issue will be back again but hope not! Great album you used for testing there.

 

[adamp]

I thought it was odd too as the values weren't wildly out of spec. but I listened to an album side after replacing the caps, but before voltage adjustments, and immediately afterward and the difference was quite profound.

The boomy bass never was intermittent in the first place, and I've listened to probably 4 or 5 records today without issues. Hopefully that's the end of it!

Adam