Display problems with TDS3014B

[perdrix]

Just bought this on eBay.  The vendor states:

On power up the image can be unstable/unreadable.  Tapping the top of the unit with your hand makes the display good.

While I'm waiting for it to arrive I thought I'd ask here if anyone has encountered this problem before and what the solution was.

Thanks
David

[JFJ]

This thread may help:

https://www.eevblog.com/forum/repair/tektronix-tds3034b-display-failure/

[perdrix]

The good news is that it arrived and the display had the odd glitch or two, but opening the beastie (what fun that is), and removing/reseating the connector from the main board to the display (and every other connector in sight), plus clearing out the dust seems to have fixed it (fingers crossed).   I tried to up-hack to TDS3064B after upgrading firmware to 3.39 but didn’t work using Keysight VISA utility .  Couldn’t get TekVisa to play 

A 9 pin null modem cable just arrived and I connected to the scope using Putty (9600,N,1 RTS/CTS) with local echo turned on:
*IDN?
TEKTRONIX,TDS 3014B,0,CF:91.1CT FV:v3.39 TDS3GV:v1.00 TDS3LIM:v1.00 TDS3FFT:v1.00 TDS3TRG:v1.00
password pitbull
mconfig tds3064b

Powered off, and then:

*IDN?
TEKTRONIX,TDS 3064B,0,CF:91.1CT FV:v3.39 TDS3GV:v1.00 TDS3LIM:v1.00 TDS3FFT:v1.00 TDS3TRG:v1.00

Checking with an SG504 shows the 3db point into 50 ohms (1Vpp in displayed .707V) is at 760MHz. 

D.