Leestereo's Restoration and Upgrade Of A Marantz 2270

[catrafter]

Any opinion on why the Marantz engineers didn't put flyback diodes for the output stage?

They did later on.

Tom

 

[hirscwi]

Nice work, Ben. It is good to read a thread that includes reason for the changes and improvements. I always learn something from your well thought out threads. Thank you.

 

[sherod]

Ben,

I increased the caps at C401 and C402 on the preamp board(P400) from .22uf to .33uf and the sound improved very nicely. Improvement was across the entire spectrum. Thanks for the recommendation.

 

[Leestereo]

@sherod: happy to hear that this small modification proved helpful. Have you replaced the ceramic capacitors on the tone control board (see post #4)? IMO, do so will provide an easily heard improvement.

 

[sherod]

I haven't done the tone board yet, but I will do it shortly. Can you provide a link for the C0G ceramics? Thanks.

 

[Leestereo]

On the P450 tone board, the replacement C0G capacitors were sourced from Mouser: 2200pF (RDE5C2A222J1S1H03A), 6800pF (RDE5C1H103J1P1H03B) and 0.01µF (RDE5C1H103J1P1H03B). HTH.

 

[sherod]

Thank you. Just a quick glance at the schematic, C451-C454 shows a capacitance of .022uf or 22,000pf and C455,456 is .006uf or 6000pf. Have you substituted those locations with different values?

 

[Leestereo]

Thank you. Just a quick glance at the schematic, C451-C454 shows a capacitance of .022uf or 22,000pf and C455,456 is .006uf or 6000pf. Have you substituted those locations with different values?

In the picture of the original board in post#4, C451-C454 are the small green capacitors, these are polyester film types; their replacements were same value polypropylene types (red WIMAs). Also, in the schematic of P450 seen in the same post, C455/C456 are shown as 0.0068µF.

 

[patfont]

As always great read! The best part is a lot can be applied to other Marantz models namely 2245/2230 which use the same pre/phono boards. On the Amp board P750 the (C751) 1uf stock cap sounds really nice, it was not until I installed a Jantzen that I felt it sounded better:





This is what I ended up with for the main filters-upgrade to screw terminals and a made from scratch buss bar:




I will definitly put some of the ideas to use, can not wait to hear your listening impressions.

 

[patfont]

Are you going to upgrade the SP locations on P700 to COG, C705/C706, C707/C708?

 

[Leestereo]

Are you going to upgrade the SP locations on P700 to COG, C705/C706, C707/C708?

Those particular ceramic capacitors are not in the signal path per se; IIRC, they are compensation capacitors for H701/H702 and H705/H706, respectively. I don't think there's much to be gained by replacing the originals with C0G types (but it wouldn't hurt either).

 

[patfont]

Thanks for clearing that up Ben, love the thought you put into this one!

 

[cortico]

Leesteero, thanks for sharing your work.
Would you recommend implementing the flyback diodes on the model 1060?

 

[Leestereo]

Would you recommend implementing the flyback diodes on the model 1060?

Since the 1060 has a capacitor-coupled output, it may be that its output transistors are protected from voltage spikes caused by the inductive kickback from the speaker coils. I think I've only seen flyback diodes installed in DC coupled amplifiers.

 

[MBuras]

I’ve documented factory installed flyback diodes installed on later model 2230’s and most recently on a late production 1060. Pictures of the 1060 below.




Mike

 

[Leestereo]

Thanks for clearing that up, Mike.

 

[Dingman]

Regarding that 150ohm\5W dropping resistor in post #2:
I have two 2270's here, and neither have that resistor installed.

Is this something added later in production? Would it be recommended to add this resistor to the units that don't have them?

 

[nj pheonix]

 

[Leestereo]

@Dingman, there are 2 variants of the regulated/protection board: one with a 150ohm/5W ceramic on the board itself (near H803) and the other variant doesn't have this resistor on the board and unit with this board have it on the tag board. Your 2270s must be using the former variant.

 

[Dingman]

Oh, OK - ya, I know what\where that 150 ohm is at on the PS\relay board. I left that one alone on both the 2270's I'm working on.
Thanks.