Recapping 3D80 What’s involved?

[Perrin21]

What parts are required for this? How difficult is it? What does it cost to do? My 3D80 has lost most of its volume.

 

[blu_fuz]

Takes some time.
Takes some parts.
DIY cost is low.
Hired out labor is high.
How do you know it needs a re-cap?

 

[Helmar]

C503 LR 2x 10 uF 16,0 V
C504, C533 LR 4x 220 uF 16,0 V
C506, C509, C535 LR 4x 470 uF 16,0 V
C532 LR 2x 47 uF 10,0 V
C536 LR 2x 2200 uF 10,0 V
C538 1x 1000 uF 6,3 V

Upgrade C605 to 6800 uF

Cost ca. 5-8€
2 hours of work on the circuit board
You need a desoldering pump 2-3 €

 

[caution]

A bad volume level is a resistance or switch/contact issue. Bad caps just cause crackling and buzzing.

 

[Helmar]

A bad volume level is a resistance or switch/contact issue. Bad caps just cause crackling and buzzing.

Both can be the case in general, yes. However the resistors do not deteriorate over the years that much, same as the sliding pots which are quality ones on the 3Ds.
If you read the service manual you can easily find out that e. g. C536 and C605 will have a huge impact on sound quality. Especially the C536s are in the high output signal path. In case they dry out sound level and quality will suffer heavily.

 

[Perrin21]

A bad volume level is a resistance or switch/contact issue. Bad caps just cause crackling and buzzing.

Both can be the case in general, yes. However the resistors do not deteriorate over the years that much, same as the sliding pots which are quality ones on the 3Ds.
If you read the service manual you can easily find out that e. g. C536 and C605 will have a huge impact on sound quality. Especially the C536s are in the high output signal path. In case they dry out sound level and quality will suffer heavily.

Ive turned it on today and the radio volume seems much higher than the aux input. The radio volume is fairly loud. I really don't know whats going on with this unit. Every time i connect the power something changes lol. Its almost perfect today.

Is it normal for the operation light to dim when theres bass or is this a sign of the caps failing?

https://youtu.be/SznjSYMZzkc

 

[Reli]

The volume slider on the 3D80 I just bought crackles and cuts out sometimes. The carbon traces inside sliders often go bad, especially when the grease dries up or someone sprays contact cleaner in them, which can wash out the grease.

 

[jimmyjimmy19702010]

The volume slider on the 3D80 I just bought crackles and cuts out sometimes. The carbon traces inside sliders often erode, especially when the grease dries up or when a fool sprays contact cleaner in them, which can wash out the grease.

Grease on the carbon traces?? The only bad thing contact cleaner will do is pull the grease from the plastic sliding mechanism. This can cause the plastic blocks to loose some height thus causing possible contact issues + stiff/inconsistent slider movement.

I normally use a small strip of 1mm solder to carefully apply grease inside the sliders to restore smooth movement after the contact cleaner application. As long as you don't skip the last step, slider servicing isn't too scary.

 

[Helmar]

Is it normal for the operation light to dim when theres bass or is this a sign of the caps failing?




C605 needs to be replaced. Power issue of the decoupling capacitor.

Regarding the sliders:
Usually they are (more) used and worn out at lower volume settings. The higher volume settings are usually rarely used. This can easily be tested by using aux-input at different input levels.

 

[caution]

Is it normal for the operation light to dim when theres bass or is this a sign of the caps failing?

Yes, if the light uses main power. But it can be avoided. For example the light in the C-100F never dims because it gets power from a separate winding in the transformer, so it does not get affected by anything going on over on the winding for main power.

 

[Superduper]

The power supplies on these boomboxes are unregulated. Put another way, under no load conditions voltage will be high and under load, voltage will be lower. If you were to view the system voltage with a meter under dynamic operation, you will see that it will fluctuate during heavy usage. In fact, the light behaves like a voltmeter because it's brightness reflects system voltage. As that is the nature of unregulated supplies, that will always be the case unless you can draw from either a different source (like Eric says using a design like the C100 or the M9998) or you can tap from a regulated rail and replace the bulb with one whose voltage requirement matches the regulated rail voltage.

 

[Helmar]

The 3d88 has no separate winding on the transformer.
Let it run on batteries in order to see if the symptom slightly improves.
C605 (2200 uF) is connected also if the box is running on DC input - even if there is nothing to decouple.

 

[caution]

I think you need that cap to deal with load spikes, AC or DC, although it also helps with the AC ripple and mains noise when on that input.

 

[Helmar]

Exactly!

 

[Perrin21]

Thanks for all the great info. I am going to get it recapped. Is there any upgrades i can do that will lift the power capability of the amplifier/Powersupply? I will be getting a local technician to do the work.

 

[Reli]

The volume slider on the 3D80 I just bought crackles and cuts out sometimes. The carbon traces inside sliders often erode, especially when the grease dries up or when a fool sprays contact cleaner in them, which can wash out the grease.

Grease on the carbon traces?? The only bad thing contact cleaner will do is pull the grease from the plastic sliding mechanism. This can cause the plastic blocks to loose some height thus causing possible contact issues + stiff/inconsistent slider movement.

I normally use a small strip of 1mm solder to carefully apply grease inside the sliders to restore smooth movement after the contact cleaner application. As long as you don't skip the last step, slider servicing isn't too scary.

Yeah you're right, sorry I misspoke

 

[Superduper]

Although not the ideal and best way to grease them, sliders, by their very nature, have a large slit that allows some amount of access and therefore, it is possible to re-install grease in some limited locations.

However, problems come when rotary pots are flooded with solvent in an attempt to clean them. That's because the location where grease resides is inaccessible without disassembly. Once a rotary pot loses it's silky smooth feel from having it's grease stripped during a solvent flush, it's virtually impossible to recover without disassembly.

Grease on the carbon traces?? The only bad thing contact cleaner will do is pull the grease from the plastic sliding mechanism. This can cause the plastic blocks to loose some height thus causing possible contact issues + stiff/inconsistent slider movement.

I normally use a small strip of 1mm solder to carefully apply grease inside the sliders to restore smooth movement after the contact cleaner application. As long as you don't skip the last step, slider servicing isn't too scary.

 

[Helmar]

So, just a small update from the weekend:

I found the time to test everything after replacing the caps:

The following issues are solved:
Balance is perfect now. Before the left speaker was much louder than the right one.
The 3d-Button now has a noticeable effect. Bass speakers are now moving (until their mechanical stop....)

See the shiny new caps on the pictures and my test setups.

Additionally I can say that the LEDs do not dim out - even on maximum volume.
The line-in level can be set to maximum gain (all level indicator LEDs on). the iPad does it when set to maximum volume, connected directly via RCA cable. Also I retro-fit a small bluetooth receiver which also does this.

The 3D88 is now fully functional. In my opinion the TRK-7620 (AKA 3D7) sounds a little more powerful with a little more bass.
But this is just my opinion.

Helmar

 

[Reli]

When you say Line In level can be set to maximum gain, are you saying there's an adjustment involved?

 

[Helmar]

No.
Its only that once I set the volume on the ipad/iphone to let's say 90% all level indicator LEDs are in use, meaning the input level is sufficient.