Marantz 2235B running hot

[mikje]

I just received a nice looking 2235B and fired it up. It seems to work pretty well except for a few issues. First, while in Aux mode, the right channel only works if I engage the Mono button. In Tape 1 both channels work fine. Tape two works, but it's a little scratchy. Maybe a dirty selector switch?
Secondly, the heat sink and transistors (on the right side as looking from the front) are pretty hot; too hot to touch. I turned it off for now. I'm not pushing it hard, I can talk over it in a 12 X 16 room. I'm running a pair of JBL L40's. I'm not sure how to check the DC offset or adjust it, but is that a possible cause of the heat?
Finally, the string for the tuner dial is a little loose. Any ideas on that?
Any other issues that might be worth checking into on this piece?
Thanks in advance for any suggestions.
Mike

[sakis]

you may want to check this out

vintage amplifier repair/upgrade manual

[Bigred]

Originally posted by mikje
I just received a nice looking 2235B and fired it up. It seems to work pretty well except for a few issues. First, while in Aux mode, the right channel only works if I engage the Mono button. In Tape 1 both channels work fine. Tape two works, but it's a little scratchy. Maybe a dirty selector switch?

Yup, sure sounds like it.

Secondly, the heat sink and transistors (on the right side as looking from the front) are pretty hot; too hot to touch. I turned it off for now. I'm not pushing it hard, I can talk over it in a 12 X 16 room. I'm running a pair of JBL L40's. I'm not sure how to check the DC offset or adjust it, but is that a possible cause of the heat?

No, but checking the DC offset and adjusting it wouldn't hurt. The most likely cause is excessive idle current. It could be other things like oscillation for example but your first step is to check the bias.

Finally, the string for the tuner dial is a little loose. Any ideas on that?

Make sure its routed correctly and the correct amount of wraps are around the flywheel and drum.

Any other issues that might be worth checking into on this piece?
Thanks in advance for any suggestions.
Mike

Much would depend on your abilities obviously. Some suggestions would be to give ALL the switches and potentiometers a good cleaning. Deoxit and faderlube are great products for this. Depending how the inside is, you can also give the inside a cleaning with some soft painters brushes and compressed air etc. STAY AWAY from the tuning capacitor. Just use the brush and compressed air carefully here. Lastly, the adjustments that we touched on already. You can adjust the DC-offset, bias and there is also a 35V regulator adjustment that could be checked and adjusted if necessary. CAUTION: My best advice? Remember, you have a working Receiver with what seems to be some minor problems so if your at all unsure of how to proceed, take it to someone that does. Measuring and making adjustments sounds really easy to some but all it takes is one slip or ill move to release the magic smoke. While your in there you can look for any obvious signs of problems or potential problems like bulging or leaking electrolytic caps for example. This of course has the potential to bring up an often times controversial topic of whether to recap or not. I'm gonna leave that for you to investigate and suggest that you look into the basic items discussed above.

[sakis]

was there ever a questionl ike "recaping or not recaping " to a 20 years old device ??????

jesus this is actually what i do for living !!!!! in the parts shop everybody wonder what i do with so many electro's

i do vintage service ( together with other things ofcourse )

i can tell you one thing only ....check with a capacitor meter and you will see ...

plus that often comercial amps have been kind cheapy regarding caps ....

[Bigred]

Excuse me sakis! You dont have to tell me. Thats precisely why I worded it the way I did and left it up to the OP to investigate. Short of restoring the damn thing I merely gave him the simple suggestions he asked for. Anybody who knows about electronics knows electrolytic have a life span. Why didn't you just tell him to restore the damn thing! Do you go ahead an recap every single unit that you get in for repair or do you SUGGEST that customer do it and explain why it should be done? Its a hard sell sometimes to customers when "essentially" their unit is working.

See what I mean with the controversial discussion?!?!?!?!

[sakis]

to e mail me and call me names big red .....


i see your aproach as a mistake any way

this is a forum !!!!! i cannot advertise here my job since i am located in greece and also since the nature of the forum is like that other people cannot advertise their job also .....

so what is the wise thing to do here ?????

A) explain to the person that recaping is fact
B) forget posting like you did that will arrize endless questions about recaping or not ....( especially if the originial thread comes from a NB )

finally i never call forum members "costumers" but i do see them as costumers if they ever come to my shop ......

for the reckord 99% of the costumers that bring to my shop vintage amplifiers go for complete restoring and not for just a cleaning or repair of one pot ..... do want to know why ?????

A) cause the amplifiers we restored in the past had amazing results and
B) if you clearly and properly explain to the costumer what is going to hapen to the amplifier the 99% will go for it

we make more than a living this way for years now

[Bigred]

You are clearly on glue sakis. Good day.

[sakis]

Originally posted by Bigred
You are clearly on glue sakis. Good day.

to you too my friend ..... have a cap of coffe and you may go as you please .....

[ostripper]

Wow, looks like bigred was on something more powerful than glue.. Bad day maybe

My feelings on recapping, old unit with cobwebs,nicotine,heavy
dust.. discuss the economics/virtue of repair with customer.

Newer 8-10 year old HT receiver...just change what is faulty,
regrease OP's.

OS

[mikje]

I did some adjustment on my 2235B tonight. I have all voltages where they should be according to the service manual.

I adjusted the following: Main Amp DC Offset Alignment, Idle Current, Main Amp DC Offset Readjustment, and Automatic Voltage regulator Adjustment. I have gone over everything more than once and got the voltages within spec. However, the heat-sink on the right side is still very warm; too warm to touch "comfortably."

I noticed on the PS board a few of the caps look suspect. The heat-shrink is "shrunk." These are C801, 805, 807, 808, and 809.

With all that said, does anyone have any ideas on what might be causing the amp to run so warm?

Thanks in Advance,
Mike